Updated

Lt. Gen. Igor Kirillov, the head of Russia's Nuclear, Biological and Chemical Defense Forces, and his assistant were killed during an explosion in Moscow on Tuesday, just a day after he was charged criminally by Ukraine's Security Services.

Russia's Investigative Committee said the explosive device was placed in a scooter near a residential apartment block on Ryazansky Avenue and triggered remotely, according to The Associated Press.

The bomb had the power of roughly 300 grams of TNT, according to Russian state news agency Tass.

Reuters reported that Ukraine's Security Services, also known as the SBU, claimed responsibility for the hit on Kirillov. Fox News Digital has reached out to the intelligence agency for confirmation.

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Igor Kirillov Russian head of nuclear forces

Lt. Gen. Igor Kirillov, chief of Russia's nuclear forces, and his assistant were killed in an explosion near a residential complex in Moscow on Tuesday, officials said. (The Associated Press)

"Investigators, forensic experts and operational services are working at the scene," RIC spokeswoman Svetlana Petrenko said in a statement. "Investigative and search activities are being carried out to establish all the circumstances around this crime."

Petrenko also said Russia is treating the explosion as a terrorist attack.

Crime scene after bomb detonated in Moscow

Lt. Gen. Igor Kirillov was charged criminally by Ukraine's Security Services just a day before he was killed in an explosion in Moscow. (Sefa Karacan/Anadolu via Getty Images)

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Kirillov was charged by the SBU on Monday with using banned chemical weapons on the battlefield. Several countries had also placed him under sanctions for his role in the war against Ukraine, The AP reported.

Building damaged during deadly explosion in Russia

The deadly blast took place outside a residential building on Ryazansky Avenue in Moscow, Russia, on Tuesday. (ALEXANDER NEMENOV/AFP via Getty Images)

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The SBU said it has recorded more than 4,800 uses of chemical weapons during Russia's attack on Ukraine, which began in Feb. 2022.

The Associated Press contributed to this report.