A pro-Russian paramilitary leader from eastern Ukraine, Armen Sarkisyan, was killed on Monday when a bomb tore through parts of a luxury apartment block in Moscow, state news agency TASS and other Russian media reported.

TASS called the bombing a well-planned assassination.

The bomb detonated just as Sarkisyan, accompanied by his bodyguards, entered the basement of the “Scarlet Sails” complex on the banks of the Moskva River just 12 km (7 miles) from the Kremlin, according to Russian media.

One bodyguard was killed and three more injured, Kommersant newspaper said.

“The assassination attempt on Sarkisyan was carefully planned and was ordered. Investigators are currently identifying those who ordered the crime,” TASS quoted a law enforcement official as saying.

Baza, a Telegram channel with contacts in Russia’s security services, published video showing major damage to the building’s lobby.

Reuters journalists on the scene saw shattered windows and a helicopter apparently evacuating the injured, amid a major police presence.

In December, Ukraine’s SBU security service described Sarkisyan as a crime boss in the Donetsk region, much of which has been controlled by Moscow since 2014, and said that he was officially suspected of participating in and aiding “illegal armed groups”.

It said he had formed a pro-Russian military unit made up of local convict fighters and had organised purchases of supplies for frontline units.

Mediazona, an independent Russian outlet that covers law enforcement, reported that Armenian-born Sarkisyan had been a longtime organised crime figure in the Donetsk region city of Horlivka.

In 2022, it said, he founded a pro-Russian paramilitary unit composed mostly of his fellow ethnic Armenians to fight against Kyiv’s forces.

In December, Ukraine took credit for the killing of Russian General Igor Kirillov in a bomb blast outside a Moscow apartment building. There was no immediate comment from Ukraine on Monday’s blast.