DAMASCUS, Feb. 3 (Xinhua) -- At least 13 Syrian soldiers were killed as a result of a fire exchange in northern Syria on Monday, a war monitor reported.

The Turkish forces bombarded the positions of the Syrian government forces in the countryside of Idlib Province in northwestern Syria and the countryside of the northwestern province of Latakia, killing 13 soldiers and wounding 20 others, according to the Syrian Observatory for Human Rights.

Some of the wounded are in critical conditions, the Britain-based watchdog said.

This Syrian and Turkish forces first exchanged fire after midnight, leading to the killing of four Turkish soldiers and six Syrian soldiers.

The observatory said the Turkish shelling was launched from the Turkey-controlled areas in Idlib and from inside the Turkish territories.

The Syrian army has been advancing toward the city of Saraqeb in Idlib countryside to secure the main highway connecting the capital Damascus in the south with Aleppo Province in the north.

Turkey supports the Syrian rebels in Idlib and has made several agreements with Russia over the map of control and deployment in the region including joint patrols.