An explosion in a Moscow luxury residential complex has killed one person and wounded four others, including a Ukrainian separatist fighting Kiev, Russian news agencies have reported.

State media said on Monday a former boxing official from east Ukraine who had set up a battalion to fight against Kiev, Armen Sarkisian, was among the wounded.

Russia has been hit by a string of assassinations and mysterious explosions since the start of the Ukraine-Russia war.

"One person died and four others were injured" after an "explosion," the TASS news agency reported, quoting health officials as saying that the injured were in serious condition.

Russian media initially reported that Sarkisian who headed a separatist boxing federation in the east Ukrainian city of Gorlivka was killed in the explosion, but later said he survived.

"Sarkisian is hospitalised. His condition is seen as extremely serious," the Interfax news agency quoted a law enforcement source as saying.

Ria Novosti news agency quoted an emergency services official as saying the blast was caused by an "explosive device".

According to Russian media, Sarkisian set up a battalion to fight in Ukraine in 2022.

News agencies published footage from the lobby of the building in north-west Moscow, showing a heavily damaged hall, a blown out door and broken glass.