MOSCOW — Maybe it was Islamic extremists who killed Boris Nemtsov. Or someone offended by his love life. Or agents of a Western power that will stop at nothing to disfigure President Vladimir Putin’s image and drive him from power.

Russian investigators, politicians and political commentators on state television on Saturday covered much ground in looking for the reason Nemtsov was gunned down in the heart of Moscow, but they sidestepped one possibility – that he was murdered for his relentless opposition to Putin.

Nemtsov, a 55-year-old former deputy prime minister and leading Russian liberal political figure for the past two decades, was gunned down shortly before midnight Friday as he walked across a bridge near the Kremlin with a woman.

The killing came just hours after a radio interview in which he called on Moscow residents to join an opposition rally on Sunday to protest Putin’s handling of the economic crisis and his “mad, aggressive and deadly policy of war against Ukraine.”

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, in contrast to its usual slow and grudging permission for opposition rallies.

The mourning march could serve to galvanize the beleaguered and marginalized opposition, or it could prove to be a brief catharsis after which emotions dissipate. Popular support for Putin has remained above 80 percent in recent months, despite the severe economic recession and soaring inflation.

Russia’s leading investigative agency said it was looking into several possible motives for the killing.

The first possibility, the Investigative Committee said, was that the murder was aimed at destabilizing the political situation in the country and Nemtsov was a “sacrificial victim for those who do not shun any method for achieving their political goals.”

This suggestion echoed comments by Putin’s spokesman and other Russian politicians that the attack was a “provocation” against the state.

The term “sacrificial victim” was also the same one Putin used three years ago when he warned that his political opponents were planning to kill one of their own and then blame it on his government.

The investigators said they also were considering whether there was “personal enmity” toward Nemtsov in his domestic life. State-controlled and Kremlin-friendly TV 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. The Investigative Committee said the pair was headed for Nemtsov’s apartment.

The agency also listed the possibility that the killing was carried out by Islamic extremists angered by Nemtsov’s position on the Charlie Hebdo attack in Paris or was connected to the Ukraine conflict.