Turkey, which supports several rebel groups in the area, immediately responded to the attack by hitting Syrian "regime targets", the Turkish defence ministry said on Twitter.

"We have three martyrs in Idlib, but the regime's losses are very high," Erdogan said during a speech in Ankara, without giving details.

The death toll rose after the defence ministry earlier on Thursday said two soldiers had been killed and two had been injured in the Syrian region.

The latest casualties have brought the number of Turkish security personnel killed in regime fire in Idlib this month to 20.

Despite the losses, Erdogan said developments in Idlib had taken a "favourable turn".

Backed by Russian air strikes, Damascus has pressed an offensive to take back the last rebel bastion of Idlib.

Hundreds of thousands of people have been forced to flee their homes since December in the largest displacement since the civil war in Syria broke out almost nine years ago.

The attacks on Turkish forces have caused strains between Ankara and Syria's key ally Russia.

The Turks urged the regime to pull back by the end of February from behind its military posts in Idlib.

Turkey set up 12 observation posts after a deal in 2018 with Moscow, whom Ankara has worked with closely despite being on opposite sides.

Russian diplomats and military officials were holding a second round of negotiations with their Turkish counterparts on Thursday.

Turkish Defence Minister Hulusi Akar told reporters the talks had "reached a certain point" and the outcome would be clearer later on Thursday or Friday, state news agency Anadolu reported.

"We will decide how to move forward based on that," said Akar.

The minister said Ankara sought access to the airspace above Idlib, controlled by Russia, to drones.