single 100 mm AK-100 guns instead of the twin 76 mm AK-726 weapons of the Burevestnik design. They also had a redesigned Variable Depth Sonar (VDS) installation. All of these ships were built in Kaliningrad. NATO referred to these ships as Krivak II class. (11 ships built). Project 11351 Nerey (Krivak III): These ships lacked the SS-N-14 missile system, which was replaced by a helicopter and hangar, and only one 100 mm gun at the bow of the ship. All ships were built in Kerch and were intended for the Soviet Border Troops under the KGB. Two ships remain in service with the Russian FSB Coast Guard and one ship was in service with the Ukrainian Navy until being scuttled in 2022 to avoid capture. It is believed that a single incomplete Krivak III hull (Hetman Bayda Vyshnevetsky c. 1995) from Ukraine was transferred to Russia and then to the Korean People's Navy. NATO referred to these ships as Krivak III class. (8 ships built). Project 11352/11353 (Krivak IV): This was a modernization of the Project 1135 (Krivak I) ships Leningradski Komsomolets (renamed Legkiy in 1992), Letuchiy, Pylkiy and Zharkiy of the Krivak I group. The refit involved replacing the RBU-6000 anti-submarine mortars with SS-N-25 anti-ship missiles, new radar, sonar and ECM equipment. These ships completed their refits in 1990–1992, and others were to have been modernised but the programme was cancelled with the collapse of the Soviet Union. NATO referred to these ships after their modernization as Krivak IV class. Project 11356 (): This is an advanced derivative built for the Indian Navy from 1999 to 2012. Three improved Nerey frigates were ordered by the Indian Navy on 17 November 1997. They are known as Talwar-class frigates in Indian naval service. Three more, armed with the BrahMos missile, were ordered on 14 July 2006. (6 ships built). Project 11356R/M (): Derivative of the Talwar class intended for the Russian Navy. Six ships were ordered for the Russian Black Sea Fleet under two contracts signed in 2010–2011, with the first ship laid down on 18 December 2010. However, due to the non-delivery of the Ukrainian gas-turbines, construction of frigates Admiral Butakov and Admiral Istomin was suspended in spring 2015. Despite earlier reports about the resumption of construction of the incomplete frigates, in October 2018, it was announced the frigates Admiral Butakov and Admiral Istomin will be sold to India under