Clashes between Syrian government forces and opposition fighters killed 14 rebels in a flare-up overnight along a strategic corridor between Damascus and the Lebanese border, activists said on Thursday. The fighting in Zabadani, a town near Damascus and the last rebel stronghold in the area - is part of the larger battle for control of the mountainous Qalamoun region, stretching from the Syrian capital to the border with Lebanon. President Bashar Assad’s forces, backed by Lebanese militant Hezbollah fighters, launched an offensive in Qalamoun in mid-November, ousting rebels from the area and cutting their supply routes from Lebanon. According to the Britain-based Syrian Observatory for Human Rights, which gathers reports from opposition activists on the ground, the latest bout of clashes killed 14 rebels and an unknown number of soldiers. Syrian government does not publicize its casualty figures in the 3-year-old conflict. Another activist group, The Syria-based Local Coordination Committees, said government aircraft dropped four crude bombs on Zabadani overnight. The Qalamoun region was a key supply corridor from Lebanon to opposition-held rural areas around Damascus. From there, rebels have been firing mortars into the capital, the seat of Assad’s government. While mortar attacks have subsided since the fall of two opposition strongholds in Qalamoun, rebels are still able to strike with lethal force in the heart of the capital and other cities. Syrian state news agency SANA said two teachers were wounded when mortar shells exploded near a school in the central Damascus district of Qanawat on Thursday.