Heavy fighting broke out around a Syrian military base on Friday, the Syrian Observatory for Human Rights said, in the first major violation of a ceasefire marking the Muslim holiday of Eid al-Adha. The Observatory said rebel fighters were trying to storm the base, which is less than half a mile from the main north-south highway linking Damascus to Aleppo, and President Bashar Assad's forces had fired artillery at a nearby village. Related stories: UN envoy: Syria's Assad agrees to holiday ceasefire Assad forces intensify air assaults dozens killed Khamenei: US and Israel seek to divide Muslims Assad himself made a rare television appearance on Friday, attending morning Eid al-Adha prayers in Damascus. Syrian State television showed him, smiling and seemingly relaxed, at an unidentified mosque in Damascus as the ceasefire, which both his regime and the main rebel group have conditionally accepted, took effect. The fighting that raged Friday in Syria's north illustrates the difficulty of enforcing even a limited truce coinciding with a Muslim holiday. Elsewhere across Syria, violence appeared to die down, and thousands of protesters took advantage of the lull to mount some of the largest anti-regime demonstrations in months. The truce, proposed by UN-Arab League envoy Lakhdar Brahimi and endorsed by the Security Council, is set for only the four days of the Eid al-Adha holiday, has no monitoring mechanism and no stated plans for its aftermath. Follow Ynetnews on Facebook and Twitter Receive Ynetnews updates directly to your desktop