"At this stage, we can say that one out of two helicopters was downed. We have two martyrs," Yildirim said in televised remarks, but added that there was: "no evidence (yet) in our hands to prove that it was a result of outside intervention."
On January 20, Turkey launched a military operation against the Kurdish People's Protection Units (YPG) militia in its western enclave of Afrin, backing Syrian rebels with air strikes and ground troops.
Ankara says the YPG is a "terrorist" offshoot of the outlawed Kurdistan Workers' Party (PKK), which has waged a three-decade insurgency inside Turkey and is blacklisted by Washington and the European Union.
State-run news agency Anadolu said the incident happened in the southern border province of Hatay, with private run Dogan news agency saying authorities were trying to reach the wreckage in the Kirikhan district.
However, in a posting on Twitter, Mustefa Bali, spokesman for the US-backed Syrian Democratic Forces dominated by the YPG, said a helicopter had been hit in the Rajo area of northwest Afrin, near the Turkish border.
Earlier, Erdogan said a helicopter had been shot down without saying who was responsible, admitting that such incidents were expected in times of conflict.
"Of course, these kinds of things will happen. We are in a war. We will have losses, but we will cause the other side to have losses as well," he said in a televised speech, vowing to make the perpetrators pay "a much heavier price."
On Friday, the military said one soldier was killed during clashes with the YPG the Afrin region.
Last Saturday, seven Turkish troops died in the worst single-day loss of the operation so far, with five killed in a tank attack.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)