The United States on Thursday shot down an armed Turkish drone that was operating near its troops in Syria, US official said, the first time Washington said it brought down an aircraft of NATO ally Turkey.
A Turkish defense ministry official said the drone shot down by the US-led coalition did not belong to the Turkish armed forces but did not say whose property it was.
Two US officials, speaking on the condition of anonymity, said a F-16 shot down the Turkish drone after the United States called Turkish military officials multiple times to warn them they were operating close to US ground forces.
The official said the Turkish drone was believed to be armed.
The Syrian Observatory for Human Rights and a local security source said the US-led coalition had shot down a Turkish drone near a base in northeastern Syria.
US-allied Syrian Kurdish forces said Turkish attacks had killed eight people in an escalation prompted by a bomb attack in Ankara claimed by Kurdish militants.
US support for Kurdish forces in northern Syria has long caused tension with NATO ally Turkey, which views them as a wing of the outlawed Kurdistan Workers' Party (PKK). That group claimed Sunday's attack in Ankara near government buildings.
On Wednesday, Ankara said the two attackers had come from Syria. The bombing killed both attackers and wounded two police officers. The Syrian Democratic Forces, the Kurdish-led force backed by the United States, denied the bombers had passed through its territory.
Ground operation into Syria
On Thursday, a Turkish defense ministry official said a ground operation into Syria was one option Turkey could consider. Turkey has mounted several previous incursions into northern Syria against the Syrian Kurdish YPG group.
"Our only goal is to eliminate the terrorist organizations that pose a threat to Turkey. A ground operation is one of the options to eliminate this threat, but it is not the only option for us," the official said.
Security forces in northeastern Syria said Turkey had launched a series of attacks on Thursday with more than 15 drones entering the region's airspace and hitting targets including infrastructure and gas and oil stations.
In a statement, the security forces said Turkish attacks killed six members of the internal security forces in northeastern Syria, and two civilians in two separate strikes.
Turkey has redoubled its operations targeting the outlawed PKK, by carrying out air strikes in northern Iraq.
Turkish officials said any infrastructure and energy facilities in Iraq and Syria controlled by the PKK, as well as People's Protection Units (YPG), were legitimate military targets.
"The PKK and the YPG are the same terrorist organization, they are our legitimate target everywhere. Turkey conducted operations whenever and wherever necessary in the past, and these operations will continue if needed again," the defense ministry official said.
"These operations are being conducted under self-defense rights arising from international law to eliminate terrorist attacks on Turkish territory and to ensure border security."
The YPG is also the spearhead of the main ally of the US-led coalition against Islamic State. Support for the YPG by the United States and other allies, including France, has strained ties with Ankara.
Turkey has warned forces of third countries to stay away from facilities controlled by the PKK and YPG.
"We are calling on all parties, our friendly and allied countries in particular, to stay away from those terrorists. This is just a reminder. It is up to them to take necessary precautions," the official said, without naming any country.