A top Russian general accused by Ukraine of being responsible for the use of chemical weapons against Ukrainian troops was assassinated in Moscow by Ukraine's SBU intelligence service on Tuesday morning in the most high-profile killing of its kind.

Lieutenant General Igor Kirillov, who was chief of Russia's Nuclear, Biological and Chemical Protection Troops, was killed outside an apartment building along with his assistant when a bomb hidden in an electric scooter went off, Russia's Investigative Committee, which probes serious crimes, said.

An SBU source confirmed to Reuters that the Ukrainian intelligence agency had been behind the hit. "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.

The source said that a scooter containing explosives was detonated, killing both Kirillov and his aide, as they stepped out of a building on Ryazansky Prospekt in Moscow.