Turkey's president has announced that a Turkish military helicopter was "downed" in northern Syria during Ankara's offensive on Syrian Kurdish militia in the region.
The Turkish military said two soldiers were killed when their attack helicopter crashed and was destroyed.
A spokesman for the Kurdish militia, Mustafa Bali, said his fighters brought down the aircraft in Raju, north-west Afrin.
President Recep Tayyip Erdogan did not mention by name the Syrian Kurdish People's Protection Units, or YPG, but said those responsible will pay.
In a video posted online by the YPG-dominated Syrian Democratic Forces, a helicopter is seen flying over a tree-lined hill and another helicopter is captured during its crash.
A helicopter is seen firing two rockets in the area as plumes of smoke from the crash rise over the trees.
After Mr Erdogan declared "one of our helicopters was also downed," the Turkish prime minister said the cause of the helicopter's crash was not yet clear and investigations were ongoing.
"We don't have exact evidence or document to determine that it went down with any outside interference," said Binali Yildirim.
Turkey launched a military offensive on January 20 to oust the YPG from Afrin, citing national security.
Turkey considers the group a terrorist organisation and an extension of an insurgency within its own borders that has fought for Kurdish autonomy for more than three decades.
Twenty one Turkish soldiers have died since the beginning of the operation.
Syria has been gripped by a new and escalating round of violence in recent weeks.
Aside from the Turkish offensive in Afrin, the Syrian government escalated its attacks on two of the largest and most important remaining opposition-held areas, in Idlib province in north-western Syria and on eastern Ghouta, a region near the capital Damascus.
Hundreds have been killed and wounded in the violence as the Syrian government and its allies sought to consolidate their hold on remaining opposition-controlled areas.
The UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein has urged urgent international action, saying the past week in Syria "has been one of the bloodiest periods of the entire conflict."
The commissioner said the "no-holds-barred nature" of the assault included attacks on nine medical facilities and the death of 277 civilians between February 4 and February 9 in both Idlib and eastern Ghouta.
There were also reports of the government using toxic agents in residential areas.
In eastern Ghouta, nearly 400,000 residents are trapped by a tightening government siege and the violence. At least two million people live in Idlib, the largest area controlled by the opposition.
"Even by Syria's atrocious standards, these are exceptionally deplorable developments - and a cruel irony given that both have been declared 'de-escalation areas'," said Mr Al Hussein.
Both Idlib and eastern Ghouta are part of Russia-negotiated de-escalation areas, which are meant to freeze the lines of conflict and allow in humanitarian aid.
Mr Al Hussein said the prevailing climate of impunity and the paralysis of the UN Security Council, divided between allies and foes of the Syrian government, calls for the Syrian conflict to be referred to the International Criminal Court, and a more concerted effort by the parties involved to bring about peace.
"The conduct and management of this war has been utterly shameful from the outset, and the failure to end it marks an epic failure of global diplomacy," said Mr Al Hussein."
The president of Turkey has announced that a military helicopter was shot down in northern Syria during Ankara's offensive against Syrian Kurdish militia there.
Speaking in Istanbul, President Recep Tayyip Erdogan did not mention by name the Syrian Kurdish People's Protection Units or YPG, but said those responsible will pay for it.
The Turkish military has not made a statement.
A spokesman for the Kurdish militia, Mustafa Bali, confirmed his fighters shot down the chopper in Raju, north-west Afrin.
Turkey launched a military offensive on January 20 to uproot the YPG from Afrin.
Turkey considers the group an extension of an insurgency within its own borders.
Nineteen Turkish soldiers have died since the beginning of the operation.