The Organization for the Prohibition of Chemical Weapons, which is leading the U.N.-backed mission to rid Syria of its chemical weapons program, said last week it would consider using the highway to transport Syria's arsenal to the port of Latakia before the weapons are taken out of the country for destruction.
Dutch diplomat Sigrid Kaag, who leads the joint United Nations-OPCW mission in Syria, said the highway was closed recently as she visited the port of Latakia in a helicopter.
"To get the material to port, it is necessary that roads are open and are safe and secure to use," Kaag said last week.
The UN-OPCW team in Syria aims to remove the most toxic chemicals from Syria by the end of the year for destruction at sea and destroy the entire program by mid-2014.
Sunday's fighting focused in the town of Nabek near the Lebanon border. Syrian troops backed by members of Lebanon's Hezbollah group managed to capture most of the town in heavy fighting, the Observatory said.
Al-Mayadeen and Al-Manar aired videos from inside the town showing bodies of fighters in the streets as well as four booby-trapped vehicles.
The Observatory said the bodies of three children, a woman and a young man who were shot dead in Nabek were brought Sunday afternoon to the nearby town of Yabroud. It said they were killed by government forces.
Opposition activist Hadi Abdullah posted a photo on his Twitter account showing two boys and a girl who he said were killed in Nabek.
In Lebanon, Hezbollah announced that two of its members, including a local commander, were killed while "performing their jihadi duties." The group did not say where the men were killed although it is widely believed to have been in Syria.
Leaflets handed out in the southern port city of Sidon identified the two as Khalil Diaa and local commander Ali Bazzi. A photo distributed in Sidon of Bazzi, showed a man with a white beard wearing a camouflage military uniform and a green beret.
Also in Lebanon, the Lebanese army captured seven Syrians Sunday who had weapons with them as they tried to cross the border.
Lebanon's National News Agency said three Syrians were detained near the Lebanese border town of Arsal while on their way to Qalamoun. It said the three were detained after midnight Sunday and had light weapons and telecommunications equipment with them.
The Lebanese army later issued a statement saying troops detained another four Syrians who were trying to cross from Syria to Lebanon in a car that had no license plate. It said the soldier found weapons, including several hand grenades, in the car.
The army said the four were detained near Arsal after they crossed into Lebanon.