The fate of Syria’s northwestern Idlib province has deepened divisions between the Russian and Turkish presidents after Syrian regime forces advanced in Hama’s countryside.
Government forces have pounded the south of Idlib province and nearby Hama with air and ground attacks this week.
Friday's advance ends opposition presence in Hama. The northwest corner is all that remains in opposition hands after more than eight years of war.
Russian President Vladimir Putin and his Turkish counterpart, Recep Tayyip Erdogan, on Friday agreed to "activate mutual efforts" regarding the situation in opposition-run Idlib province, the Kremlin said in a terse statement.
But according to Turkey’s presidency, Erdogan told Putin that Syrian army attacks in northwest Syria are causing a humanitarian crisis and threaten Turkey's national security.
Erdogan will discuss developments in northwestern Syria in a phone call with US President Donald Trump in the coming days, it said.
It added that the Turkish president will make a one-day official visit to Russia on August 27.
The recent advances by Assad's forces have put Turkish troops stationed in the region in the firing line.
"Regime forces have surrounded the Turkish observation post in Morek after capturing other towns and villages in this pocket," said the Syrian Observatory for Human Rights.
But Turkish Foreign Minister Mevlut Cavusoglu denied it, saying “our observation point there is not cut-off and nobody can isolate our forces and our soldiers."
He called for an immediate end to the fighting but said that Turkish troops were staying put at the Morek observation post out of choice – not necessity.
"We are there not because we cannot get out, but because we do not want to get out. We are there in accordance with the deal we made with Russia,” Cavusoglu told a news conference in Lebanon.