A top Russian general accused by Ukraine of being responsible for the use of chemical weapons against Ukrainian troops has been assassinated in Moscow using a bomb hidden in an electric scooter, Russian investigators said on Tuesday.

Lieutenant General Igor Kirillov, who was chief of Russia's Nuclear, Biological and Chemical Protection Troops, was killed outside an apartment building on Ryazansky Prospekt along with his assistant, Russia's Investigative Committee, which probes serious crimes, said in a statement.

An agency source claimed the Security Service of Ukraine carried out a special operation to kill Kirillov, regarded by Kyiv as a war criminal and an "absolutely legitimate target," accusing him of ordering the use of prohibited chemical weapons against Ukrainian forces in the war.

"The liquidation of the chief of the radiation and chemical protection troops of the Russian Federation is the work of the SBU," the source said, explaining that a scooter containing explosives was detonated when Kirillov and his assistant entered the entrance of a building on the Ryazansky Prospekt in Moscow. 

Dmitry Medvedev, deputy chairman of Russia's Security Council, responded that the Ukrainian leadership would face imminent revenge for the killing of a top Russian general, RIA news agency reported.

"Realising the inevitability of its military defeat, it launches cowardly and despicable strikes in peaceful cities," Medvedev reportedly said.

Shattered entrance

Photographs posted on Russian Telegram channels showed a shattered entrance to a building littered with rubble and two bodies lying in the blood-stained snow.

Reuters footage from the scene showed a police cordon. Investigators said they had opened a criminal case into the murder of two servicemen. Law enforcement sources told Russian media it was likely to be upgraded into a terrorism case.

Russia denies Ukrainian allegations it uses chemical weapons on the battlefield and Kirillov, who was married with two sons, was himself sometimes shown on state TV accusing Ukraine of violating nuclear safety protocols.

Britain in October imposed sanctions on Kirillov and his nuclear protection forces for using riot control agents and over multiple reports of the use of the toxic choking agent chloropicrin on the battlefield.

There was no immediate official comment on his murder from Ukraine, where state prosecutors were reported on Monday to have charged Kirillov in absentia with the alleged use of banned chemical weapons, the Kyiv Independent cited the Security Service of Ukraine as saying.

Russia has accused Ukraine of carrying out a string of targeted assassinations on its soil since the start of Moscow's full-scale conflict with Ukraine in February 2022.

The most high-profile cases include the 2022 killing of Darya Dugina, the daughter of Russian nationalist ideologue Alexander Dugin, in a car bomb attack, the murder of pro-war blogger Vladlen Tatarsky in a 2023 cafe bombing and the shooting last year of a Russian submarine commander accused of war crimes by Kyiv.

Russia's radioactive, chemical and biological defence troops, known as RKhBZ, which Kirillov commanded are special forces who operate under conditions of radioactive, chemical and biological contamination and who are tasked with protecting ground forces operating in extreme conditions.