During the unrest in Ukraine in the aftermath of the 2014 Ukrainian revolution, the city of Mariupol, in Donetsk Oblast, saw skirmishes break out between Ukrainian government forces, local police, and separatist militants affiliated with the Donetsk People's Republic. Government forces withdrew from Mariupol on 9 May 2014 after heavy fighting left the city's police headquarters gutted by fire. These forces maintained checkpoints outside the city. Intervention by Metinvest steelworkers on 15 May 2014 led to the removal of barricades from the city centre, and the resumption of patrols by local police. Separatists continued to operate a headquarters in another part of the city until their positions were overrun in a government offensive on 13 June 2014. Background Mariupol is the second-largest city in the Donetsk Oblast, and has experienced sporadic unrest since March 2014. Pro-Russian and anti-government groups first occupied the city council building on 18 March 2014. The first violent incident had occurred during the night on 16 April 2014, when about 300 pro-Russian and anti-government protesters attacked a Ukrainian military unit in Mariupol, throwing petrol bombs. Internal Affairs minister Arsen Avakov said that troops were forced to open fire, resulting in the killing of three of the attackers. Ukrainian government forces claimed they "liberated" the Mariupol city council on 24 April 2014, though this was heavily disputed by anti-government demonstrators, and a BBC report said that there was "no sign" of the army. The building changed hands multiple times thereafter, but was captured by the army on 8 May. Events A violent clash involving armoured personnel carriers (APC) took place at the Mariupol police headquarters on Victory Day, 9 May 2014. The Ukrainian government said it sent in the APCs in response to an attempt by militant separatists to storm the building. According to the Internal Affairs Ministry, the assault on the station involved 60 separatists armed with automatic weapons. Some local policemen reportedly helped the militants during the takeover and later clashed with Internal Troops who fired on the building with heavy machine guns mounted on the APCs. The Ukrainian government said its contingent included police, as well as an Omega unit of the National Guard. Pro-Russian protesters attempted to stop the advance, but were unsuccessful. Ukrainian security forces attacked the police headquarters in an attempt to recapture it from militants, and during the assault the building caught fire. According to Internal Affairs minister Arsen Avakov,