Insurgents in Iraq say they have killed four Russian embassy workers kidnapped at the start of June.
The Russians were seized in Baghdad's Mansour district
The Mujahideen Shura Council, an umbrella group incorporating al-Qaeda in Iraq, released an internet video and a statement announcing their deaths.
The video showed one man being beheaded and another shot dead, as well as the body of a third, but there was no sign of the fourth hostage.
Russia said it recognised its diplomats but could not confirm their deaths.
"This footage is not new. It dates from mid-June. It featured members of staff of our embassy, who named themselves, and that was indeed them," said Foreign Minister Sergei Lavrov.
"The same video also contained footage of an execution of several people. But we cannot say with 100% certainty that these are our people," he said.
"Experts possessing the necessary equipment and experience are now studying the footage as thoroughly as possible," he added.
The men were seized in Baghdad on 3 June, and kidnappers said the executions were in revenge for "torture, killing and displacement by the infidel Russian government" in Chechnya.
The Mujahideen Shura Council, which said it was holding the men, had threatened to kill them if Russia did not pull its troops out of Chechnya.