All Turkey's border gates with Syria are to be closed from Wednesday, an official from the Turkish Customs and Trade Ministry told Reuters, in response to worsening security conditions.
Syrian rebels seized control of several gates on the Syrian side of the frontier over the last week.
The closure will halt the passage of vehicles between Turkey and Syria. Refugees from Syria, who have been fleeing into Turkey in their thousands to escape the conflict, cross the border through smuggling routes.
Tensions along the border were fuelled by the shooting down last month of a Turkish military reconnaissance jet by Syrian air defences.
Ankara, which previously had close ties with Damascus, subsequently increased its military presence, sending anti-aircraft missiles to the border and scrambling planes when Syrian aircraft came close to Turkish territory.
Wednesday's move will close the only three border gates that were still open, at Cilvegozu, Oncupinar and Karkamis, the unnamed official said.
The official said Customs and Trade Minister Hayati Yazici would make an announcement on the decision at 0800 GMT.
Crossing the border had become increasingly hazardous for truck drivers involved in trade between the two countries. They faced the constant risk of being targeted by combatants or caught in the crossfire between the two sides.
Turkish Prime Minister Tayyip Erdogan said this week the uprising against Assad was "closer than ever to victory" and warned Turkey will respond firmly to any hostility from Syria.
Turkey has called for Assad to quit after he failed to heed calls for reform and the country has harboured Syrian rebels and tens of thousands of refugees along its border with Syria.
Meanwhile, Syria's envoy to Cyprus Lamia Al Hariri has defected and is now in Qatar, a member of the opposition Syrian National Council (SNC) said on Wednesday.
"Yes, she has defected and is in Doha," SNC member Wael Merza told Reuters by phone.
11 men executed by Syrian forces in Damascus
Syrian activists, who provided video of men with bullet holes in the side of their heads, said they found on Wednesday the bodies of 11 men who were executed by forces loyal to President Bashar Al Assad in the Damascus district of Qaboun.
Footage showed 11 bloodied bodies, some in an alleyway and some inside a building. Three appeared to have been shot through their shirts, which were pulled above their heads, and one was kneeling against a wall.
Rania Al Midani, an opposition activist who lives near Qaboun, said that the men were arrested five days ago in a nearby district.
"Activists found them today in Tishreen alley. They thought these men were in jail. They could only enter the alleyway today to find their bodies as it was previously occupied by (pro-Assad militia) shabbiha," she told Reuters over Skype.
Assad's forces and plain-clothed shabbiha militiamen are accused of several massacres, including the May 25 killing of at least 108 people, nearly half of them children, in Homs province, which was later verified by United Nations monitors on the ground.