An explosive device planted close to a residential apartment block in Moscow killed the head of Russia’s Nuclear, Biological, and Chemical Defence Forces, Lt. General Igor Kirillov, early on Tuesday, Russia’s Investigative Committee said.

Kirillov’s assistant also died in the blast, triggered by the device which was placed in a scooter, officials said.

Russian investigators have opened a case into the two deaths, according to the committee's spokesperson Svetlana Petrenko.

“Investigators, forensic experts and operational services are working at the scene,” she said in a statement.

“Investigative and search activities are being carried out to establish all the circumstances around this crime.”

Kirillov, who had been in his post since 2017, was sanctioned in October by Britain over the alleged use of chemical weapons in Ukraine. (Agencies)