A senior Russian officer, Lieutenant General Vladimir Alexeyev, was rushed to hospital after being shot in Moscow on Friday, officials said.
Alexeyev is deputy chief of the Main Directorate of the General Staff at the Defense Ministry.
When mercenary chief Yevgeny Prigozhin staged a short-lived mutiny in June 2023, Alexeyev was one of the top officials who were sent to negotiate with him.
The Moscow prosecutor's office said Alexeyev had been shot several times at a residential building in northwest Moscow by an unidentified assailant who fled the scene.
Investigative Committee spokesperson Svetlana Petrenko didn’t say who could be behind the attack on Alekseyev.
Several senior Russian officers have been assassinated since the start of the war in Ukraine, with Moscow blaming the attacks on Kyiv. In some cases, Ukrainian military intelligence has claimed responsibility.
The most recent officer to be killed was the head of the General Staff's army training directorate, Lieutenant General Fanil Sarvarov, who was killed by a bomb under his car on December 22.
Friday’s attack came a day after Russian, Ukrainian and US negotiators wrapped up two days of talks in Abu Dhabi. The Russian delegation was led by the military intelligence chief, Adm. Igor Kostyukov.