Turkey threatened Saturday to strike back if its military outposts in the Syrian opposition bastion of Idlib come under attack, a day after officials said three had been surrounded.

Under an agreement with Russia, a key ally of Syrian President Bashar al-Assad, Turkey has set up 12 observation posts in Idlib to avert an offensive by Syrian government forces.

Since Friday, Turkey has sent 350 vehicles with commandos backed by armoured vehicles to beef up the positions, the state-run Anadolu news agency said, after officials reported that three had been surrounded by regime forces.

"Our observation posts in Idlib continue their duties and are capable of protecting themselves with the weapons and equipment they possess," the Turkish defence ministry said on Twitter.

"In the event of a new attack, a proper response will be given in the strongest manner, based on the right of self-defence."

President Recep Tayyip Erdogan has given Syria an ultimatum to pull its troops away from Turkish observation posts by the end of February, after eight Turks were killed by regime fire on Monday.

Turkey has deployed 350 vehicles with commandos backed by armoured vehicles to reinforce observation outposts in the Syrian opposition bastion of Idlib
Turkey has deployed 350 vehicles with commandos backed by armoured vehicles to reinforce observation outposts in the Syrian opposition bastion of Idlib AFP / Aref TAMMAWI

Fahrettin Altun, Erdogan's top press aide, said the escalation in Idlib was becoming unacceptable for Ankara, and blamed Assad's regime for the crisis.

"We cannot tolerate what has been unfolding in Idlib. We will seek accountability for our martyrs," he told a Turkey-Syria media forum on Saturday in Istanbul.

"Bashar al-Assad's place in the future ... is not the presidential palace but the International Court of Justice at The Hague," he said.

Since the deadly clashes erupted, Turkey has urged Moscow to convince Assad to end the Syrian offensive.

A Russian delegation was to meet Saturday with Turkish officials to discuss the situation.

Turkey and Russia have worked closely in recent years to resolve the standoff in Idlib despite being on opposing sides of the conflict.