DAMASCUS: A ceasefire came into effect in the early hours of Friday after the Syrian army and main rebel force fighting to oust Bashar al-Assad’s regime agreed to down arms for a four-day Muslim holiday.

The Syrian Observatory for Human Rights said calm followed a night of fierce clashes nationwide, including in the Damascus area, in second city Aleppo and in the center of the country near the border with Lebanon.

The truce took hold with morning prayers kicking off the Eid al-Adha feast at the end of the hajj pilgrimage, and state television showed President Assad attending a Damascus mosque, smiling and chatting with worshippers.

The fragile ceasefire was immediately tested, however, as security forces opened fire at anti-regime protests that followed morning prayers marking the start of Eid.

The protests took place in Damascus and its suburbs, in second city Aleppo, in the northeast in Deir Ezzor and Raqa and at Inkhel in the south, where three people were injured, according to activists and the Observatory.

Regime forces and the Free Syrian Army (FSA) said on Thursday that they would follow UN-Arab League peace envoy Lakhdar Brahimi’s call for the temporary ceasefire, but both reserved the right to respond to any aggression.

If the ceasefire holds it would be the first real breakthrough in halting—even temporarily—the 19-month conflict that rights groups say has killed more than 35,000 people in Syria.