Ukraine says it is responsible for the explosion in Moscow that killed the head of Russia's defense forces

The head of the Nuclear, Biological, and Chemical Defense Forces, Lt. General Igor Kirillov was killed along with his deputy on Tuesday when a bomb exploded in Moscow, Russia's Investigative Committee said. Ukrainian security sources told CBS News that the Security Service of Ukraine (SBU) killed Kirillov in a special operation. The claim could not be independently verified.

Sources said a scooter with explosives was detonated when Kirillov and his aide entered a residential building.

“Kirillov was a war criminal and a legitimate victim, as he ordered the use of illegal chemical weapons against the Ukrainian military,” a source with knowledge of the SBU told CBS News. “Such a terrible fate awaits everyone who kills the people of Ukraine. Retribution for war crimes is inevitable.”

The deputy chairman of the Security Council of Russia, Dmitry Medvedev, said that the leaders of Ukraine will immediately take revenge for the murder, reported the Russian media RIA.

The bomb was detonated remotely and contained 300 grams of TNT, Russian news agency Tass reported, citing unnamed sources in the emergency services.

“Investigators, intelligence experts and operatives are working at the scene,” Svetlana Petrenko, spokeswoman for Russia's National Investigative Committee, said in a statement. “Investigations and searches are underway to establish all the circumstances surrounding this crime.”

He also said that the Kremlin was treating it as a terrorist attack.

Kirillov and the unit he led have been sanctioned by several countries, including the UK, Canada and the US, for using chemical weapons in Ukraine.

Ukraine's SBU said it has recorded more than 4,800 instances of Russia using chemical weapons on the battlefield since President Vladimir Putin launched his all-out attack in February 2022. In May, the US State Department announced sanctions on Kirillov's unit, which the US said was a record. the use of chloropicrin, a poison gas first used in World War I, against Ukrainian soldiers.

Kirillov has been in his post since April 2017, AFP noted.

Russia has denied using any chemical weapons in Ukraine and, in turn, has accused Kyiv of using toxic agents in the war.

Kirillov was convicted in absentia by a Ukrainian court on December 16 of using chemical weapons banned in Ukraine during Russian military activity in Ukraine which started on Feb. 2022.

Nearly three years into Russia's ongoing war in Ukraine, Russian forces have made small but steady advances, adding to roughly one-fifth of Ukraine they already control.

Emmet Lyons contributed to this report.