The head of the Russian military’s biological and chemical weapons unit, Lt. Gen. Igor Kirillov, was killed along with his deputy early Tuesday in an explosion in Moscow, Russia’s Investigative Committee said. Ukrainian security sources told CBS News that the Security Service of Ukraine (SBU) killed Kirilov in a special operation. The claim could not be independently verified, but Russian officials quickly vowed to retaliate against Ukrainian leaders.

Sources said the explosive scooter was detonated near Kirilov and his aide outside a residential building in the Russian capital. Video circulating online showed two men exiting the building just before an electric scooter parked near the entrance exploded.

“Kirillov was a war criminal and an absolutely legitimate target, as he gave orders to use banned chemical weapons against the Ukrainian military,” an informed source in the SBU told CBS News. “Such an inglorious end awaits all those who kill Ukrainians. Retribution for war crimes is inevitable.”

Russian Security Council Deputy Chairman Dmitry Medvedev said Ukrainian leaders would face immediate retaliation for the killing, Russian news agency RIA reported.

The bomb was detonated remotely and had a force equivalent to approximately 300 grams of TNT, Russian state news agency Tass reported, citing unnamed sources in the emergency services.

“Investigators, forensics and operational services are working at the scene,” Svetlana Petrenko, a spokeswoman for Russia’s National Investigative Committee, said in a statement. “Investigative and search actions are being carried out to establish all the circumstances of this criminal act.

She also said that the Kremlin is 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, over the use of chemical weapons in Ukraine.

Ukraine’s SBU said it had recorded more than 4,800 instances of Russia using chemical weapons on the battlefield since President Vladimir Putin launched his full-scale invasion in February 2022. In May, the US State Department announced sanctions against Kirillov’s unit, saying the US had recorded the use of chloropicrin, a poisonous gas first used in World War I, against Ukrainian troops.

Kirilov, who has been in the post since April 2017, has also been accused by the US government of helping spread disinformation about biological weapons and research.

In March 2023, about a year later A full-scale Russian invasionthe said the US State Department Kirilov “significantly increased his media engagement” to issue repeated, unsubstantiated claims that the US government was involved in the creation of mpox and COVID-19, and that the US was “developing biological weapons that can selectively target ethnic groups”.

“The US government is concerned that this fake story could be a prelude to false-flag operationwhere Russia itself uses biological, chemical, or nuclear weapons in Ukraine and then tries to blame Ukraine and/or the United States,” the State Department said at the time.

Russia has denied using any chemical weapons in Ukraine and in turn has accused Kiev of using toxic agents in combat.

On December 16, Kirilov was sentenced in absentia by a Ukrainian court for the use of chemical weapons banned in Ukraine during Russian military operation in Ukraine which started in February 2022.

Almost three years into the ongoing Russian war, Russian troops are made small but steady progressadding to the nearly one-fifth of Ukraine they already control.

Since Russia invaded, several prominent figures have been killed in targeted attacks believed to have been carried out by Ukraine.

Darja Dugina, a commentator on Russian TV channels and the daughter of the nationalist ideologue Alexander Dugin connected to the Kremlin, killed in a car bomb explosion in 2022 which investigators suspected was aimed at her father.

Vladlen Tatarsky, a popular military blogger, died in April 2023when the statuette that was given to him at the party in St. The Russian woman, who said that she gave the figurine as a gift at the behest of a contact in Ukraine, was convicted and sentenced to 27 years in prison.

In December 2023, Illia Kiva, a former pro-Moscow Ukrainian MP who fled to Russia, was shot and killed near Moscow. Ukraine’s military intelligence service praised the killing, warning that other “traitors of Ukraine” would share the same fate.

On December 9, a car bomb in the Russian-occupied Ukrainian city of Donetsk killed Sergei Yevsyukov, the former warden of Olenivka prison where dozens of Ukrainian prisoners of war were killed in a July 2022 rocket attack. Another person was injured in the explosion. Russian authorities said they had arrested a suspect in the attack.

Editor’s note: This article has been updated to reflect that the Russian military unit formerly led by Kirilov does not control the country’s nuclear weapons, as previously noted, but only its biological and chemical weapons.

contributed to this report.