Tensions escalated Tuesday as a Syrian military helicopter was shot down and Ankara warned of a “heavy price” for any attacks on its forces.
The new flare-up, a day after regime shelling killed five Turkish troops, came as government forces battling rebels in northwestern Syria took full control of a key highway linking the country’s four largest cities.
A rocket attack downed a Syrian regime helicopter in Idlib province, killing both pilots, an AFP correspondent and a war monitor said.
Syrian state news agency SANA confirmed the downing of the aircraft and the killing of its crew, saying it was caused by a rocket fired from a part of Idlib where Turkey-backed rebels operate.
The Britain-based Syrian Observatory for Human Rights said the helicopter was hit by a rocket fired by Turkish forces, though Ankara did not claim responsibility.
Turkey, which has troops deployed in several locations in northern Syria, continues to support rebel groups battling the Assad regime or acting as proxies against Kurdish forces.
Along with regime ally Russia, it is the key foreign broker in northern Syria, but a 2018 deal aimed at averting a major offensive has failed to take hold.
On Tuesday, Erdogan said Turkish troops would continue to respond to Syrian regime attacks.
“The more they attack… our soldiers, they will pay a very, very heavy price,” he told a televised ceremony in Ankara.
Erdogan said he would reveal his next steps on Wednesday.
The Syrian army hit back in a later statement saying it was “ready to respond to the aggressions of the occupying Turkish army”, accusing Ankara of targeting its positions with rockets.
US Secretary of State Mike Pompeo said Washington would work with Turkey on its response to Monday’s attack.
“The ongoing assaults by the Assad regime and Russia must stop,” Pompeo said on Twitter.
He said he had sent US special envoy for Syria James Jeffrey to Turkey “to coordinate steps to respond to this destabilising attack”.
The Idlib region is a dead-end for hundreds of thousands of people who were forced to flee or were evacuated from formerly rebel-held territory elsewhere in Syria.
Some have moved four times or more since the start of the war but there is nowhere for them to go after Idlib, with the Turkish border to the north and government forces in the other three directions.
“Existing camps and settlements of internally displaced persons are overcrowded, and shelter in existing houses is getting scarce,” the UN refugee agency said Tuesday.