A pro-Russian warlord who gained infamy for abusing Ukrainian prisoners of war has been assassinated in Donetsk.

Mikhail Tolstykh, who went by the nom-de-guerre Givi, was reportedly killed by an explosion in his office on Wednesday morning (8 February), in what pro-Russian insurgents have blamed on Ukrainian operatives.

The rebels' Donetsk News Agency said a rocket was fired from a portable launcher into his office. Russian state television showed footage of firefighters putting out flames at the building said to be his headquarters.

Tolstykh, 35, was from Donetsk and before the conflict served as a tank commander in the Ukrainian army before he joined the rebel forces. He eventually became a commander in the so-called Donetsk People's Republic (DPR).

His guerrilla battalion, named Somali, participated in fierce battles including the siege of Donetsk airport. He became infamous for mocking wounded Ukrainian prisoners in 2015 and faced sanctions from the European Union for mistreatment of prisoners of war. The news outlet 112 reported that he had his arm amputated recently after an injury he had suffered in action.

A number of separatist commanders have died recently, which has been blamed on Ukrainian attacks. Kiev has refused to negotiate with such warlords whom it regards as terrorists.

The Moscow Times reported that there are also conspiracy theories that commanders who have become too independent are being killed at Moscow's behest. An explosion in an elevator killed the insurgent leader Arseny Pavlov, also known as Motorola, in October 2016. Earlier in the year, the commander Alexei Mozgovoi was bombed.

The Associated Press reported that now the rebel-controlled parts of the Donbass have come to be controlled by bureaucrats with links to the ousted pro-Russian President Viktor Yanukovych, who are thought to be more open to striking a deal with Kiev.

It follows a spike of violence, which saw at least 27 people killed after a week of violence in Avdiivka, which borders Donetsk.

The principal deputy chief monitor for the Organisation for Security and Co-operation in Europe (OSCE), Alexander Hug, said that the heavy weapons moved into the area, against the Minsk agreement, had increased tensions in the region.

"At the moment the sides are holding down fire but the root cause of the presence of heavy weapons and the close proximity has not been dealt with and this leads to permanent fighting and the fighting affects the civilian areas here significantly," he told ITV News.

Ukraine conflict
Tanks are seen near the government-held town of Bakhmut, Ukraine. The pro-Russian commander Mikhail Tolstikh was reportedly killed in an explosion Reuters