Igor Kirillov, a general in charge of Russia’s military’s nuclear and chemical weapons protection forces, was killed on Tuesday by a bomb in Moscowps88, the Russian authorities said.

An official with Ukraine’s security service, known as the S.B.U., said that Ukraine was responsible for the killing. The official, who spoke on the condition of anonymity to discuss a sensitive intelligence operation, confirmed the details of the assassination given by Russia.

General Kirillov, 54, died along with an aide after an explosive device planted in a scooter was detonated on Tuesday morning near the entryway to a residential building, Russia’s Investigative Committee, a law enforcement agency, said in a statement.

The explosion occurred at about 6:12 a.m. and shattered windows in a building across the street, according to RIA Novosti, a Russian state news agency.

A day before his killing, Ukraine had accused General Kirillov of criminal activity, saying he was responsible for the “massive use of banned chemical weapons” in Ukraine. The security service said that Russian forces had used chemical weapons on the battlefield more than 4,800 times since the war began, on General Kirillov’s orders. Russia denied Ukraine’s accusations during a July meeting of the Organization for the Prohibition of Chemical Weapons.

Ukraine has said the chemical weapons used by Russia often include combat grenades equipped with the irritant chemical agents CS and CN. Those tear gases, most commonly used by riot police officers to control crowds, are banned in warfare under the Chemical Weapons Convention, an arms control treaty ratified by more than 150 countries, including Russia.

The U.S. State Department said this spring that Russia had used chloropicrin, a choking agent widely used in World War I, as well as tear gas on the battlefield. Britain imposed sanctions on General Kirillov this fall, citing his responsibility in deploying chemical weapons in Ukraine.

According to Russia’s military, the division that General Kirillov oversaw carries out specialized tasks like protecting Russian troops when chemical and nuclear weapons are used.

General Kirillov was also prominent in Russia’s propaganda campaign against Ukraine and the West, frequently addressing the news media and appearing on television with unfounded claims. In 2023, he said that the United States was planning to use drones “designed to spread infected mosquitoes.”

Dmitri A. Medvedev, a former president and deputy chairman of the Russian Security Council, pledged “inevitable retaliation” against the “military and political leadership of Ukraine,” according to Tass, a state news agency.

Reporting by Anton Troianovski and Constant Méheut.

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