Ukraine’s Defence Intelligence (HUR/DIU) says its forces have damaged a Russian Project 21631 Buyan-M small missile ship in the Azov Sea near occupied Crimea, forcing the vessel to withdraw from its patrol area.

The agency published video and a written statement on 28 August describing a joint operation by its Department of Active Operations and the special unit “Prymary”.

According to DIU, fighters from “Prymary” used a precision drone to disable the ship’s radar, after which special forces struck the vessel itself. DIU said the ship was operating in Temryuk Bay — described as a potential launch area for Kalibr cruise missiles — and left its station after sustaining “significant damage”. The statement did not name the ship. Russia had not issued a public comment at the time of publication.

Ukrainian and independent outlets amplified the announcement, citing DIU’s statement and footage. Kyiv-based media reported that the target was a Buyan-M-class small missile ship, a type associated with Kalibr strikes since 2022.

Buyan-M ships (Project 21631) are short-range missile corvettes equipped with an eight-cell UKSK 3S14 vertical launcher that can fire Kalibr cruise missiles, among other munitions. Open-source specifications list the class at about 75 metres in length and roughly 950 tonnes displacement, with a 100mm A-190 main gun and close-in air defences. Their shallow draft and riverine mobility allow redeployment between seas via inland waterways.

The operation has prompted debate among Ukrainian commentators over the means used. DIU did not disclose the specific drone type. Analysts and media in recent weeks have highlighted Ukraine’s growing use of first-person-view (FPV) attack drones in maritime environments — including demonstrations of boat-launched FPVs — and long-range “Bober” (UJ-26) drones employed by DIU in other theatres. While those developments indicate a broader expansion of Ukrainian uncrewed strike options, their direct use in the Temryuk Bay attack has not been confirmed by DIU.

DIU framed the location as operationally relevant, saying the ship was within a zone from which Kalibr missiles could be launched. Since the start of the full-scale invasion, Russia has repeatedly used Kalibr from surface vessels for long-range strikes. In March 2022, for example, a Buyan-M corvette launched eight Kalibr missiles in a publicly released strike video.

The report of the Azov Sea strike coincided with a large-scale Russian aerial attack on Kyiv and other locations overnight into 28 August. Officials said at least 19 people, including four children, were killed in the capital, and dozens were injured. The European Union Mission’s premises and the British Council site in Kyiv sustained damage, prompting protests from the EU and UK. Moscow claimed it targeted military infrastructure.

If confirmed, the damage to a Kalibr-capable platform would be notable in the context of Ukraine’s broader campaign against Russian naval assets around the Black Sea and the Sea of Azov, which has used a mix of aerial and maritime drones, electronic warfare and stand-off weapons. Ukraine argues that degrading launcher platforms constrains Russia’s ability to mount large missile salvos against cities and infrastructure. Independent assessment of the ship’s repair timeline or any impact on Russia’s near-term strike capacity was not available.

As of Thursday afternoon, DIU had released no details on casualties among the Russian crew or on the vessel’s subsequent movements beyond saying it left the patrol area. Russia’s Defence Ministry had not issued a statement addressing DIU’s specific account.

Background on the class: Project 21631 Buyan-M ships are designed for littoral operations and, unusually for vessels of their size, carry vertical launch systems able to fire land-attack missiles. Sources list eight UKSK cells and a standard fit including a 100mm main gun and close-in weapons. The combination has made the class a frequent launcher for Kalibr strikes, including from sheltered waters.