MOSCOW (AP) — A car bomb killed a Russian general on Monday, the third such killing of a senior military officer in a year. Investigators said Ukraine may be behind the attack.

Lt. Gen. Fanil Sarvarov, head of the Operational Training Directorate of the Russian Armed Forces’ General Staff, died from his injuries, said Svetlana Petrenko, the spokesperson for Russia’s Investigative Committee, the nation’s top criminal investigation agency.

“Investigators are pursuing numerous lines of inquiry regarding the murder. One of these is that the crime was orchestrated by Ukrainian intelligence services,” Petrenko said.

Since Moscow sent troops into Ukraine nearly four years ago, Russian authorities have blamed Ukraine for several assassinations of military officers and public figures in Russia. Ukraine has claimed responsibility for some of them. It has not yet commented on Monday’s death.

Kremlin spokesman Dmitry Peskov said that President Vladimir Putin had been immediately informed about Sarvarov’s killing.

The Defense Ministry said that Sarvarov had previously fought in Chechnya and taken part in Moscow’s military campaign in Syria.

Just over a year ago, Lt. Gen. Igor Kirillov, the chief of the military’s nuclear, biological and chemical protection forces, was killed by a bomb hidden on an electric scooter outside his apartment building. Kirillov’s assistant also died. Ukraine’s security service claimed responsibility for the attack.

An Uzbek man was quickly arrested and charged with killing Kirillov on behalf of the Ukrainian security service.

Putin described Kirillov’s killing as a “major blunder” by Russia’s security agencies, noting they should learn from it and improve their efficiency.

In April, another senior Russian military officer, Lt. Gen. Yaroslav Moskalik, a deputy head of the main operational department in the General Staff, was killed by an explosive device placed in his car parked near his apartment building just outside Moscow. A suspected perpetrator was quickly arrested.

Days after Moskalik’s killing, Ukraine’s President Volodymyr Zelenskyy said he received a report from the head of Ukraine’s foreign intelligence agency on the “liquidation” of top Russian military figures, adding that “justice inevitably comes” although he didn’t mention Moskalik’s name.