Turkey on Wednesday (February 5th) issued Syria an ultimatum, demanding that the regime pull its forces back from military posts in the Idlib region following unprecedented clashes between their forces this week.

The escalation between Turkish and Syrian troops -- which saw more than 20 people killed in exchanges on Monday -- is testing the uneasy relations between Turkey and Russia, the key foreign brokers of the conflict.

"If the regime does not pull back, Turkey will be obliged to take matters into its own hands," Turkish President Recep Tayyip Erdogan said, giving Syria until the end of the month to comply.

Erdogan had on Tuesday warned that his country would not allow Syrian regime forces to gain more ground and accused them of driving "innocent and grieving people" towards the Turkish border.

But Syrian regime forces were continuing their offensive in Idlib province on Wednesday -- one which has killed 300 civilians since December and displaced some 520,000 people in one of the biggest upheavals of the nine-year war.

Regime presses offensive

Regime forces have seized more than 20 towns and villages from opposition groups and extremist alliance Tahrir al-Sham over the past 24 hours, according to the Syrian Observatory for Human Rights.

The Observatory said Russian airstrikes killed three civilians -– all members of the same family -– on the outskirts of Idlib city on Wednesday.

Regime rocket fire killed another civilian in the town of Anjara in the west of Aleppo province.

Erdogan said two of Turkey's 12 observation posts in Idlib, set up under a 2018 agreement with Russia, were now "behind the regime's lines".

The post at Morek was surrounded by Syrian regime forces in December, while another at Surman now lies within the regime's area of control.

Erdogan called on Moscow, the key backer of the Syrian regime, to "better understand our sensitivities in Syria".

He spoke with his Russian counterpart Vladimir Putin on Tuesday and told him Ankara would respond "firmly" to any new Syrian attack.

The US on Tuesday threw its support behind Turkey over its reprisals against the Syrian army.

Secretary of State Mike Pompeo called the mortar attack on Turkish posts in Idlib "a grave escalation" and said US officials "fully support Turkey's justified self-defence actions in response".