Syrian rebels fought fierce clashes with loyalist troops Saturday as they tried to secure their supply line to second city Aleppo against advances by the army, a monitor said.
The clashes in the divided area of Handarat just north of Aleppo, came a day after fighting that killed 15 soldiers and pro-regime militia as well as 12 rebels, said the Syrian Observatory for Human Rights.
"Rebels from all the main factions have launched an operation to try to secure the Handarat area," said Observatory director Rami Abdel Rahman.
"They are trying to expel the army from hills captured by the regime in recent days," Abdel Rahman told AFP.
Earlier this month the Observatory reported that government troops backed by fighters from Lebanese Shiite movement Hezbollah took Handarat, just north of Aleppo.
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The battle for control of Handarat hill is decisive for the rebels as the position overlooks their main supply route from Turkey and because it could place rebel areas of Aleppo under army siege.
"Should the army take over the whole area, it could bring rebel areas of Aleppo city under total siege," said Abdel Rahman.
Aleppo has been divided since a rebel offensive in summer 2012 between loyalist sectors on its west side and rebel territory on the east.
The rebels launched an offensive on Aleppo in July 2012, bringing several districts under their control. Fighting in the now ravaged city has mostly ground to a stalemate.
Abdel Rahman said fighters on the regime side in Handarat also include Iranians and Palestinians from a pro-government militia.
Syria's war began as a peaceful movement demanding democratic change, but morphed into an all-out war after President Bashar al-Assad's regime launched a brutal crackdown against dissent.
More than 180,000 people have been killed since March 2011, and nearly half of the population has been forced to flee their homes.