Syrian rebels Saturday declared the failure of a truce declared for Eid al-Adha, as fighting raged, warplanes buzzed key cities and at least 150 people were reported killed since a ceasefire came into effect.

The truce conditionally agreed by President Bashar al-Assad's regime and the rebel Free Syrian Army (FSA) on Thursday had raised the prospect of the first real halt to the fighting after 19 months of conflict.

But the first day Friday of Eid -- one of the most sacred holidays in Islam -- saw the ceasefire shattered by fresh fighting, deadly car bombings and a new regime vow to hunt down "armed terrorists", its term for rebel fighters.

Fighting raged again on Saturday and regime warplanes were reportedly seen flying over the embattled northern city of Aleppo after a brief lull for the start of Eid.

An AFP correspondent said a warplane was also seen flying over Damascus on Saturday.

A rebel commander in Aleppo said there was no doubt the ceasefire initiative, proposed by UN-Arab League envoy Lakhdar Brahimi, had fallen apart.

"This is a failure for Brahimi. This initiative was dead before it started," Abdel Jabbar al-Okaidi, head of the FSA military council in Aleppo, told AFP by telephone.

He insisted the FSA had not broken the ceasefire and was only carrying out defensive actions.

"I was on several fronts yesterday and the army did not stop shelling," Okaidi said. "Our mission is to defend the people, it is not us who are attacking."

The Eid holiday had started with a slowdown in the fighting -- and state television footage of Assad smiling and chatting with worshippers at a Damascus mosque -- but quickly degenerated.

The Syrian Observatory for Human Rights, a key monitor of the conflict, said 146 people were killed in bombings and fighting on Friday, including 53 civilians, 50 rebels and 43 members Assad's forces.

On Saturday, fresh violence killed at least 13 people, the Observatory said, amid clashes and attacks in Damascus province, Aleppo, Daraa in the south and the eastern city of Deir Ezzor.

Among them were five killed in a car bomb attack in Deir Ezzor, it said. State television blamed the attack on "terrorists" and said the bomb had gone off in front of a church, causing significant damage.

According to the Observatory, more than 35,000 people have been killed in the conflict, which began as an anti-regime uprising but is now a civil war pitting mainly Sunni rebels against Assad's regime dominated by his minority Alawite sect, an offshoot of Shiite Islam.

The Britain-based Observatory relies on a countrywide network of activists, lawyers and medics in civilian and military hospitals. It says its tolls take into account civilian, military, and rebel casualties.

Assad's forces and the FSA had both agreed to a call by Brahimi to lay down their arms for the four-day Eid, but both also reserved the right to respond to attacks.

Brahimi had hoped the truce might lead to a more permanent ceasefire during which he could push for a political solution and bring aid to stricken areas.

Okaidi, the FSA commander in Aleppo, said the ceasefire had been doomed from the start and that the international community needed to stop putting faith in the regime.

"The Syrian people have become guinea pigs, every time there is an envoy who tries an initiative, while we know the regime will not respect it."

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