MOSCOW — Russia’s top investigative body said Saturday it is looking into several possible motives for the killing of prominent opposition figure Boris Nemtsov, including an attempt to destabilize the state, Islamic extremism, the Ukraine conflict and his personal life.

A statement from the body, the Investigative Committee, did not address the possibility seen as likely by many of Nemtsov’s supporters — that he was killed for being one of President Vladimir Putin’s most adamant and visible critics.

The 55-year-old Nemtsov was gunned down Friday near midnight as he walked on a bridge near the Kremlin with a female companion. The killing came just a few hours after a radio interview in which he denounced Putin’s “mad, aggressive” policies and the day before he was to help lead a rally protesting Russia’s actions in the Ukraine crisis and the economic crisis at home.

After his death, organizers canceled the rally and instead called for a demonstration to mourn him on Sunday in central Moscow. The city gave quick approval for that gathering, in contrast to its usual grudging permission for opposition rallies.

The Investigative Committee said it was looking into whether Nemtsov had been killed as a “sacrificial victim for those who do not shun any method for achieving their political goals,” a suggestion echoing the comments by Putin’s spokesman and other Russian politicians that the attack was a “provocation” against the state.

It also said it was considering whether there was “personal enmity” toward him in his domestic life. State-controlled TV and Kremlin-friendly media outlets on Saturday gave considerable attention to Nemtsov’s companion, identifying her as a Ukrainian model 30 years his junior and showing photos of her in alluring poses.