Turkish and Russian troops held their 20th joint patrol along the key M4 highway in Syria’s northwestern province of Idlib, Turkey’s Defense Ministry announced, according to Anadolu Agency.

“According to the Turkey-Russian Federation Agreement/Protocol; 20th TR-RF Combined Land Patrol on M-4 Highway in Idlib, comprising the entire route between Trumbah and Ayn Al Havr, was conducted with the participation of land and air elements,” the ministry said in an official statement.

The M4 highway, also known as the Aleppo-Al Hasakah road, is about 30 kilometers (19 miles) from Turkey’s southern border.

This March, Ankara and Moscow agreed on a protocol urging parties to “cease all military actions along the line of contact in the Idlib de-escalation area.”

The protocol said joint Turkish-Russian patrols would begin on March 15 along the M4 highway from the settlement of Trumba — 2 km (1.2 mi) west of Saraqib — to the settlement of Ain al-Havr.

Idlib has long been under siege by Assad regime forces and its allies, and previous cease-fires for the region were plagued by violations.

Turkey has worked to protect the local civilian population as well as rid the wider region of terrorist elements.