An explosive device planted close to a residential apartment block in Moscow killed the head of Russia’s Nuclear, Biological, and Chemical Defence Forces, Lieutenant General Igor Kirillov, early today, 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.

The bomb was triggered remotely, Russian state news agency Tass reported, citing unnamed sources in the emergency services.

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."

Ukraine’s Security Services on December 16 charged Kirillov with the use of banned chemical weapons during Russia’s military operation in Ukraine that started in February 2022.

Ukraine’s Security Service, the SBU, said that they had recorded more than 4800 uses of chemical weapons on the battlefield since February 2022, particularly K-1 combat grenades.

In May, the US State Department also said in a statement that it had recorded the use of chloropicrin, a chemical weapon first used in World War I, against Ukrainian troops.

Kirillov, who was named the head of Russia’s nuclear defence forces in April 2017, was under sanctions from several countries including the UK and Canada for his role in Ukraine.

During the almost three-year operation, Russia has made small but steady territorial gains to the nearly one-fifth of Ukraine it already controls.