President Recep Tayyip Erdogan met Russian Defence Minister Sergey Shoigu in Istanbul on Sunday.
The meeting, which was closed to the press, included Turkish National Defense Minister Fikri Isik, Chief of General Staff General Hulusi Akar, National Intelligence Organisation head Hakan Fidan and Turkish presidential spokesman Ibrahim Kalin.
Turkish and Russian leaders agreed in May that the relations between the two countries are progressing "beyond normalisation", after deteriorating in 2015 when a Russian fighter jet was shot down for violating Turkish airspace.
Since then, the countries have lifted most economic sanctions and trade barriers.
The two countries, along with Syrian opposition and regime leaders, are also working to stabilise the situation in Syria and stop the bloodshed at the upcoming Astana talks in Kazakstan,
The fifth round of talks to resolve Syria's six-year civil war will begin in Astana in two days' time.
At the fourth meeting in the Kazakh capital on May 4, the three guarantor countries: Russia, Turkey and Iran, signed a deal to establish de-escalation zones in Syria.
"Currently, together with Iran and Turkey, we are completing work on documents that define the boundaries of the de-escalation zones and procedures for their control and operation," Shoigu said on Friday, according to a Russian Defence Ministry statement.