Any normalization between Ankara and Damascus would reshape the decade-long Syrian war.

Turkey's intelligence chief held multiple meetings with his Syrian counterpart in Damascus over the last few weeks, a sign of Russian efforts to encourage a thaw between states on opposite sides of Syria's war, four sources said.

A regional source aligned with Damascus told Reuters that Hakan Fidan, head of Turkey's National Intelligence Organization (MIT), and Syrian intelligence chief Ali Mamlouk met as recently as this week in the Syrian capital.

The contacts reflect a Russian policy shift as Moscow steels itself for a protracted conflict in Ukraine and seeks to secure its position in Syria, where its forces have supported Syria's President Bashar al-Assad since 2015, according to two Turkish officials and the regional source.

Any normalization between Ankara and Damascus would reshape the decade-long Syrian war.

Turkish backing is vital to sustaining Syrian rebels in their last major territorial foothold in the northwest, after Assad defeated the insurgency across the rest of the country, aided by Russia and Iran.

But rapprochement faces big complications, including the fate of rebel fighters and millions of civilians, many of whom fled to the northwest to escape Assad's rule.

Turkey, a NATO member country, has troops on the ground across the area, deemed occupying forces by Assad.

During the meetings, Fidan - one of Turkish President Tayyip Erdogan's closest confidants - and Mamlouk evaluated how the two countries' foreign ministers could eventually meet, according to a senior Turkish official and a Turkish security source.

"Russia wants Syria and Turkey to overcome their problems and achieve certain agreements...which are in the interest of everyone, both Turkey and Syria," said the Turkish official.