Yıldırım said it remains "unclear" why the helicopter went down and added that an investigation had been launched.
However, pro-Kurdish news sources said it was shot down in the village of Qude in Afrin's Rajo district.
Earlier, President Recep Tayyip Erdogan said a helicopter had been shot down without saying who was responsible.
The Turkish military said in a statement that two soldiers were killed when its attack helicopter crashed and was destroyed at around 1 p.m. local time (10 a.m. GMT).More news: Barcelona coach Valverde calm after Getafe stalemate
Turkey launched a military offensive on January 20 to oust the YPG from Afrin, citing national security.
"At this stage, we can say that one out of two helicopters was downed".
"We are in a war".
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.
Turkey opened a new front in the multisided Syrian civil war, when it launched an air and ground offensive against YPG fighters on its southern border with Syria last month.More news: Turnover: Cavaliers overhaul roster with stunning series of trades
The Turkish military uses the term "neutralized" in reference to terrorists captured dead or alive, or those who surrender during the operations.
Four more Turkish soldiers have been killed in northern Syria, the Turkish military announced late Saturday, bringing the day's death toll to 11 in what has been the most lethal day since Ankara's offensive on Syrian Kurdish militia began.
Erdogan has promised to sweep the militia from Turkey's southern border, a move that could put Turkish troops in confrontation with US forces on the ground in Syria.
In a statement, the military said the Turkish Armed Forces had destroyed 19 YPG targets and "neutralized" 86 more militants during operations since February 10. Seven Turkish civilians have also lost their lives.More news: S. Korean president's approval rating stays high ahead of Winter Olympics
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