Across the EU and the UK, the picture that emerges is not a single monolithic menace but a layered ecosystem: transnational jihadist organisations with global franchises; state sponsors and proxies that blur the line between espionage and terrorism; entrenched separatist movements that ebb and flow; and ideologically driven extremists on the far right and far left.

Europol’s latest Terrorism Situation and Trend Report (TE-SAT 2025) still judges the overall terrorist threat to the EU “acute,” with jihadist terrorism the principal concern, while also tracking right-wing, left-wing/anarchist, and separatist violence and plots.

The UK’s security service gives the broad taxonomy succinctly: the primary threats are Islamist terrorism, extreme right-wing terrorism, and Northern Ireland–related terrorism, with smaller volumes of left-wing/anarchist and single-issue extremism. That blend has persisted even as the operational tempo and actors evolve.

Who is active now?

ISIS and affiliates—especially ISIS-K

Islamic State’s “brand” remains the most dangerous transnational vector. The core organisation has lost territory but not intent; its external operations model relies on online guidance, remote facilitation, and low-tech methods. More worrying for European services is ISIS-Khorasan (ISIS-K), which intelligence assessments repeatedly flag as the most dynamic and ambitious external-operations node in the ISIS network, with a track record of mass-casualty attacks in the broader region and explicit interest in Western targets. DNI+1

UN and European reporting in 2024–25 underscores how ISIS and aligned actors exploit instability—from Syria and Iraq to the Sahel and Afghanistan—while using digital platforms for recruitment, fundraising and tradecraft. That strategic depth matters to Europe because permissive sanctuaries generate propaganda, money flows, and operational know-how that seep into European cells and lone actors.

Al-Qaeda’s ecosystem

Al-Qaeda’s central organisation remains less noisy than ISIS but endures via affiliates (AQAP, AQIM, al-Shabaab). Its European threat is slower burn: fewer plots, but persistent inspiration and capability seeds—bomb-making tradecraft, targeted-killing guidance—transmitted online or via travellers. Assessments still include al-Qaeda actors in the risk calculus for Europe’s aviation, diplomatic, and Jewish/community targets.

Iran, Hezbollah, and state-linked plots on European soil

A notable shift in 2024–25 has been the prominence of state-linked hostile activity that shades into terrorism: assassination, kidnap, sabotage and intimidation targeting dissidents and perceived regime enemies. The UK’s MI5 has publicly stated that, since January 2022, British authorities have disrupted around twenty Iran-backed plots posing potentially lethal threats to UK residents—a blunt statement that moves this from conjecture to fact. The UK Parliament’s Intelligence and Security Committee has likewise characterised Iran as one of the most significant state threats to UK safety, detailing kidnap/assassination risks and overseas killings in Europe.

That state nexus matters because it intersects with proscribed groups and proxies. The UK fully proscribes Hezbollah; the EU lists its “military wing.” Operationally, European services focus less on labels and more on behaviours: surveillance of diaspora communities, pressure on journalists and activists, and use of criminals for deniable acts—phenomena police chiefs across the UK have publicly warned about.

Hamas networks and fallout from Middle East flashpoints

Hamas is a designated terrorist organisation in both the EU and the UK; the Israel–Hamas war has raised the risk of lone-actor and networked plots aimed at Jewish targets in Europe as well as threats to public events. Europol’s 2025 trend reporting highlights how global conflicts are exploited by multiple actors for mobilising narratives—something seen across Islamist, right-wing, and left-wing milieus.

PKK in the European theatre

The PKK remains proscribed by the EU and UK, and European countries repeatedly grapple with PKK-linked fundraising, internal discipline violence, and clashes at demonstrations. While the PKK’s main theatre is Turkey/Iraq/Syria, its European footprint—political activism, financing, intimidation—keeps it on security radars.

Dissident Irish republican groups

The “New IRA” remains the principal Northern Ireland–related terrorist threat. The 2023 shooting of DCI John Caldwell in Omagh—claimed by the group—was a stark reminder that dissident networks retain both intent and capability; court proceedings in August 2025 describe further planning around that attack. That translates to a sustained UK threat line running alongside Islamist and far-right cases.

Extreme right-wing networks and lone actors

Right-wing terrorism in Europe skews toward small networks and lone actors radicalised online, frequently inspired by transatlantic manifestos and accelerationist propaganda. TE-SAT data over recent years records a steady trickle of disrupted plots, weapons seizures, and online incitement, with occasional cross-pollination with gun culture and militia fantasy. The UK treats extreme right-wing terrorism as a standing priority alongside Islamist and Northern Ireland–related threats.

Extreme left-wing/anarchist violence

While far less lethal than in the 1970s–80s, pockets of left-anarchist militancy persist—especially arsons and IEDs targeting property, infrastructure, and political offices in parts of southern Europe. Europol tracks this stream precisely because it endures at low level and periodically spikes around summits, trials, or policing incidents.

Dormant—or seemingly dormant—threats that still matter

Europe’s “legacy” groups can fade from headlines without disappearing:

• ETA (Basque Country) and Corsican FLNC: the former has disbanded; the latter oscillates. Residual networks, weapons caches, and fundraising means the risk isn’t zero, particularly of splinter violence in response to political shocks. (Europol keeps separatism as a category for good reason.)

• RAF/Action Directe–style far-left terrorism: the era of West German or French urban guerrillas is over, but the mythology still feeds micro-cells and justifies sabotage campaigns. TE-SAT’s inclusion of left-anarchist incidents is a reminder that dormant ideologies can animate opportunistic violence.

• Al-Qaeda central: reduced visibility is not elimination. Patience, propaganda and opportunistic external operations remain part of its model. Western intelligence community outlooks for 2025 still list AQ alongside ISIS as a global threat actor. DNI

The bigger “dormant” worry is less organisational than environmental: prisons, refugee routes hijacked by smugglers, and conflict spillover (Ukraine, Middle East, Sahel) create recruitment opportunities and weapons flows that can re-energise flagging networks.

Motives: religion, politics, and the allure of grievance

• Religiously framed jihadism remains the top lethal risk, combining apocalyptic ideology with a simple operational grammar (knives, vehicles, improvised weapons) and digital command-and-influence. The propaganda mixes religious claims with hyper-political grievances over Gaza, Western foreign policy, and social alienation.

• Politics-first separatism (dissident Irish republicanism; PKK) is motivated by sovereignty and identity, often wrapped in historic narratives of occupation and resistance. Such groups fundraise and propagandise across European diasporas even when domestic tempo dips.

• Ideological extremism on the right and left thrives on online subcultures: accelerationism, eco-nihilism, anti-system conspiracism, and anti-police animus. Many perpetrators are “do-it-yourself” terrorists who consume a global stew of memes rather than follow strict command structures. Europol and MI5 both flag this self-starter dynamic.

• State-directed coercion (not always labelled terrorism in statutes) uses terror-like methods—especially targeted violence—to silence dissidents and project intimidation abroad. The UK intelligence community has publicly set out Iran’s kidnap/assassination model, and police have described a sharp rise in such life-threatening operations by hostile states.

Laws, labels and the contested space of “support”

The UK and EU maintain lists of proscribed organisations under law. Proscription matters: it criminalises membership, material support and the “glorification” of terrorism. The UK keeps an extensive roster (jihadist, right-/left-wing, separatist), and EU listings include the likes of ISIS, al-Qaeda, Hamas and the PKK (and Hezbollah’s military wing at EU level; the UK proscribes Hezbollah in full). These frameworks shape policing and speech boundaries and help distinguish sharp political advocacy from impermissible support.

Public argument about “support” turns incendiary when it intersects with elected figures. A well-documented example is Jeremy Corbyn’s 2009 reference to members of Hamas and Hezbollah as “friends”—a formulation he later told MPs he regretted using. The 2018 controversy over his presence at a Tunis commemorative ceremony—held in an area near graves of figures linked by critics to Black September—further fuelled debate; Corbyn said he was there to honour victims of a 1985 Israeli airstrike and denied honouring terrorists. These are matters of public record and remain highly contested in political discourse.

The wider European debate features similar flashpoints: appearances at rallies where proscribed symbols surface; platforming of speakers accused of justifying violence; and fundraising or “solidarity” campaigns that risk straying into unlawful support. The legal line—especially post-October 7—has tightened in many jurisdictions, and prosecutors have been more willing to test it.

What’s changed since 2023—and what hasn’t

Three shifts stand out in 2024–25:

1. The rise of state-linked plots on European soil. UK authorities have been unusually explicit about Iran-linked threats, and European services report similar patterns. That draws counter-terrorism, counter-espionage and public-order policing onto the same chessboard.

2. ISIS-K’s external posture. Assessments from Western intelligence communities continue to warn about ISIS-K’s demonstrated capability and intent to strike outside its home theatre, keeping European cities inside its ideational blast radius even when plots are crude.

3. The “polycrisis” multiplier. War in Ukraine, violence in the Middle East, coups across the Sahel, energy shocks and migration pressures give extremists of all stripes narrative oxygen. Europol’s TE-SAT and related briefings emphasise how terrorists exploit exactly these global tensions.

What hasn’t changed is the operating system of European counter-terrorism: granular intelligence work, legal disruption (arrests and proscription offences), and a focus on lone-actor prevention through community reporting and online monitoring. The UK’s formal threat levels, and their categories from “Low” to “Critical,” remain the background hum of risk communication—even when the day-to-day barometer shifts.

Where to focus next

• Hardening against lone-actor simplicity. Most plots aim for low-tech feasibility: knives, vehicles, improvised weapons. This argues for relentless local policing, community liaison, and fast disruption of intent signals online. Europol

• Relentless pressure on logistics and money. Whether PKK, ISIS facilitators, or state proxies, finance and travel are their arteries. TE-SAT’s repeated stress on arrests and financing cases suggests this is where steady attrition pays off. Europol

• Clearer policy on state-terror interfaces. The kidnapping/assassination problem requires diplomatic, legal and covert responses—plus decisions on designations (for instance, debates about proscribing the IRGC) that have strategic consequences. UK parliamentary oversight bodies have urged more coherence here.

• Civic resilience for high-salience targets. Jewish communities, faith venues, police/military personnel, transport hubs, and major events remain priority targets across ideologies. Hardened security and rapid response save lives even when prevention fails.

Bottom line

Europe and the UK do not face a single “wave” of terrorism so much as overlapping ripples—some visible, some subsurface—that can combine into dangerous surges. The marquee names—ISIS, al-Qaeda—still matter, particularly via ISIS-K. Old causes—dissident republicanism, the PKK—haven’t vanished. State actors now overtly inject coercive violence and intimidation into Europe’s domestic space. And ideological extremism online continues to mint self-starter terrorists faster than any proscription list can be updated.

The response is as unglamorous as it is necessary: meticulous intelligence work, legal discipline, international cooperation, and political sobriety. The data in 2025 doesn’t justify complacency. It does, however, show that quiet disruption—arrests, court cases, interdicted money flows, and exposed plots—remains Europe’s most effective counter-terrorism success story.