Turkish forces in Syria may have fired live ammunition into a crowd of protesters during a joint patrol with Russian troops, killing some of the demonstrators.
Video obtained by Reuters shows protesters hurling rocks at the convoy.
But a group that monitors the war in the UK, the Syrian Observatory for Human Rights, says that two protesters were killed and seven injured when the Turkish soldiers fired on them.
It could not be independently verified and a witness to the incident told Reuters that only three people were wounded at the scene, without mentioning any dead.
The witness also said that the soldiers first fired their guns into the air in an attempt to disperse the protesters, before they fired on them.
Tear gas was also used, according to the witness.
The defense ministries of Turkey and Russia have not confirmed any casualties.
Turkey says a patrol was conducted safely for military and civilians, quote, "despite provocation by terrorists."