Buyan-class corvette

Initial information about a modified Project 21631, dubbed Buyan-M, was published in August 2010. The Project 21631 ships were to be an updated variant of the Project 21630 Buyan small artillery ships. They were to be up-armed with a USKS VLS system supporting the nuclear-capable Kalibr cruise missiles (SS-N-27 Sizzler) and with additional electronic countermeasure equipment. Ships of Project 21631 were designated for national economic zones protection, same as the original variants.

The ships' small size and displacement enables them to operate within inland river systems, including traversing the Moscow Canal. This allow them to redeploy to various seas around European Russia. A particular advantage for the Buyan-M series were the limitations imposed by the Intermediate-Range Nuclear Forces Treaty (INF) which prohibited land-based medium-range missiles while sea-based ones were not restricted. A river-based corvette could deploy such missiles without being subject to the restrictions.^{[citation needed]} The lead ship of this project, Grad Sviyazhsk, was laid down on 27 August 2010 and commissioned on 27 July 2014.

On 7 October 2015, corvettes Grad Sviyazhsk, Uglich, Velikiy Ustyug and Gepard-class frigate Dagestan, deployed in the Caspian Sea, launched 26 Kalibr cruise missiles at 11 terrorist targets in Syria. The missiles flew nearly 1,500 kilometres (930 mi) over Iran and Iraq and struck targets in Raqqa and Aleppo provinces (controlled by the Islamic State) as well as in Idlib province (controlled by the al-Qaeda-linked Nusra Front). According to United States Department of Defense officials, several of these cruise missiles fired from Russian ships crashed in Iran and did not make it to their intended targets in Syria.

On 20 November 2015, the same warships launched 18 Kalibr cruise missiles from the Caspian Sea at seven terrorist targets in Rakka, Idlib and Aleppo provinces.

In 2016, the corvette Zelenyy Dol was deployed to the Mediterranean Sea, later followed by sister ship Serpukhov. On 19 August Zelenyy Dol and Serpukhov, deployed in the Mediterranean Sea, launched Kalibr cruise missiles at positions of Al-Nusra terrorist group in Syria. As a result of the strikes, number of terrorist facilities were destroyed, including command post and base near the village of Dar Ta Izzah and weapon production plants and warehouses in Aleppo province.

On 25 October 2016, Zelenyy Dol and Serpukhov were deployed to the Baltic Sea to join a newly formed division at Kaliningrad. In 2020, Zelenyy Dol and the Karakurt-class corvette Odintsovo deployed to Arctic waters utilizing Russian internal waterways and illustrating the Russian capacity to transfer light units among the Russian Navy's three western fleets and the Caspian Flotilla as might be required. A similar deployment was conducted in 2023 by Serpukhov.

On 28 March 2022, a Buyan-class corvette fired eight Kalibr missiles from the Black Sea and claimed to have destroyed a Ukrainian arsenal at Orzhev.

On 17 June 2022, a photo emerged of Velikiy Ustyug being towed on the Volga River in a damaged state after a Ukrainian attack.

On 8 April 2024, Ukrainian military intelligence released a video in which they claimed to have started a fire onboard Serpukhov. The fire reportedly occurred on 7 April. Serpukhov was in harbour at Baltiysk, Kaliningrad Oblast. Ukrainian military intelligence claimed that the fire destroyed "its communication and automation systems."

• Project 21630 Buyan
• Project 21631 Buyan-M – Upgraded design with modernised systems and new weapons
• Project 21632 Tornado – Export design
• Project 21635 Sarsar – Unveiled at Army-2022 expo, with an increased number of VLS cells, as well as a larger displacement overall

• List of ships of the Soviet Navy
• List of ships of Russia by project number
• Rubin-class patrol boat

• Project 21630 - Complete Ship List
• Project 21631 - Complete Ship List