The Pentagon says United States warplanes have shot down a Turkish drone, which was deemed a threat to its forces in Syria, in an incident that might raise tensions between the NATO allies.

The development came on Thursday as Turkey targeted Kurdish forces in Syria following a suicide bombing in Ankara that was claimed by the outlawed Kurdistan Workers’ Party (PKK).

US troops observed drones carrying out raids on Thursday morning, some of them inside a “restricted operating zone” (ROZ) near Hasakah, about a kilometre (less than a mile) from Washington’s troops, Pentagon spokesman Brigadier General Pat Ryder told journalists.

A few hours later, a Turkish drone returned to the ROZ and flew towards American forces despite what a US official said were a dozen calls to Ankara’s military.

Ryder said “US commanders assessed … the UAV, which was now less than a half kilometre from US forces, to be a potential threat,” using an abbreviation for an unmanned aerial vehicle.

“US F-16 fighters subsequently shot down the UAV in self-defence,” he said.

Defense Secretary Lloyd Austin spoke with his Turkish counterpart Yasar Guler on Thursday, urging “de-escalation in northern Syria and the importance of maintaining strict adherence to de-confliction protocols and communication through established military-to-military channels,” Ryder said in a statement.

Turkey’s defence ministry confirmed the call, saying the two officials discussed “the latest developments in Syria”.

Al Jazeera’s Sinem Koseoglu, reporting from Istanbul, said the UAV did not belong to the Turkish military, according to a statement.

“It is not only the Turkish military that conducts counterterrorism operations in northern Iraq and Syria,” she said.

She said that the Turkish intelligence and interior ministry’s gendarmerie also joined operations.

Cross-border attacks

On Thursday night, Turkish military air attacks killed 26 fighters and destroyed 30 Kurdish fighter targets in northern Syria, including an oil well, a storage facility and shelters, and “neutralised” many fighters, the Turkish defence ministry said.

Al Jazeera’s Alan Fisher, reporting from Washington, said Turkish officials say operations are carried out as part of the country’s right to self-defence.

“Turkey has warned other countries to stay away from areas controlled by groups it will continue to target,” he said.

The US has about 900 troops deployed in Syria as part of international efforts to combat the ISIL (ISIS) armed group, and carries out frequent raids targeting the fighters.

US forces are partnered with the Syrian Democratic Forces (SDF), which led the fight that dislodged ISIL fighters from the last territory they held in the country in 2019.

However, Turkey views the Kurdish People’s Protection Units that dominate the SDF as an offshoot of the PKK, which is considered a “terrorist” group by Ankara and its Western allies.

Turkish attacks on military and infrastructure targets in Kurdish-held areas of Syria killed at least nine people on Thursday, according to Kurdish security forces.

Syria contains a dangerous mix of often antagonistic forces operating on the ground and in the air, including those from President Bashar al-Assad’s government, Russia, the US, Turkey, Iran-linked armed groups and the Kurdish fighters, among others.