Two deadly car bombs and sporadic fighting marred a shaky holiday truce Friday in Syria, although thousands of protesters used the brief respite in the civil war to pour into the streets and demand President Bashar al-Assad's ouster.

Chants of "Syria wants freedom!" rang out in the streets in the largest demonstrations in months, suggesting that a 19-month-old crackdown and sustained violence has not broken the spirit of those trying to rid the country of Assad's rule.

But even if a ceasefire holds for the intended four-day Muslim holiday of Eid al-Adha, it's unlikely to be a springboard for ending the conflict that has already claimed more than 35,000 lives.

Syria mediator Lakhdar Brahimi, the UN-Arab League envoy, has not charted a way forward or said how he would bridge the deep divide between Assad and his opponents. The Syrian president won't resign and the opposition says it won't negotiate a transition deal until he does.

Brahimi's plan marks the first attempt by the international community in six months to scale back the violence that has displaced hundreds of thousands of people and devastated entire neighbourhoods. A more comprehensive UN ceasefire plan in April quickly collapsed.

Brahimi did not set clear terms for the truce, perhaps to reduce the possibility of failure. He only said it should be in effect during the four-day holiday, but made no arrangements for monitoring compliance.

A few hours after the truce took effect, a car bomb in a residential area of Damascus, near a housing complex for police, killed 10 people and wounded more than 30, Syrian state media said.

Amateur video posted online showed debris scattered across a large area. Flames shot out of the car's gutted wreckage, as frantic residents tried to evacuate casualties. One rescuer carried a man with blood streaming down his face.

Another rigged car went off near an army checkpoint in the southern city of Deraa, killing three soldiers, said the Britain-based Syrian Observatory for Human Rights, which compiles reports from a network of activists.

Still, there appeared to be a drop in fighting and casualties Friday.

Daily death toll tops 150

In recent weeks, the daily death toll usually topped 150. From dawn to dusk Friday, 62 people were killed, including 24 regime soldiers, according to the Observatory.

Khaled al-Shami, an activist in Damascus, said he expected the lull to end quickly. "The regime cannot afford to give a truce a chance," he said. "The leadership worries it will breathe new life into the revolution and they will not let that happen."

However, rebel commanders have also dismissed the truce as irrelevant, while a radical Islamic group fighting on the rebel side, Jabhat al-Nusra, has rejected the ceasefire outright.

Gunmen from the group also took part in fighting Friday near a military camp close to a key supply road to Aleppo, Syria's largest city. In Aleppo, where rebels and regime forces are locked in a stalemate, fighting raged near the military airport, killing at least four people.

A Syrian rebel fighter runs for cover through a sniper line-of-fire at the Karmal Jabl front-line in the city of Aleppo. (Narciso Contreras/Associated Press)

Elsewhere, at least 22 people were killed by regime shelling and sniper fire in the Damascus suburbs of Harasta and Douma, and in the northern Idlib province, the Observatory said.

In Washington, State Department spokeswoman Victoria Nuland said the U.S. has seen violations on both sides but pointed out reports of attacks from helicopters and tanks. "These are weapons, obviously, that the opposition doesn't have," she said.

Friday's street protests in a number of locations across Syria began after worshippers emerged from mosques after holiday prayers.

Amateur videos posted online Friday showed large groups of protesters waving rebel flags, cheering, clapping or holding each other by the shoulders in traditional Arab group dances.

The videos appeared consistent with AP's reporting on the demonstrations in the area.

Shouts for freedom could be heard in the Damascus suburb of Kfarbatna. Others called out, "May God curse your soul, Hafez!" — a reference to the president's late father and predecessor.

In the rebellious Damascus suburb of Douma, protesters carried a sign that read, "Only in Syria do people wear white [burial] shrouds for the Eid." Others shouted, "You will fall, Bashar!"

In marches in the southern city of Deraa, three people were wounded when troops tried to disperse the crowd, the Observatory said.

The protests were reminiscent of the early days of the uprising against Assad, when tens of thousands of demonstrators turned out each week after services and held rallies demanding that he resign. The rebellion later turned violent as Assad's troops tried to put down the revolt, and such protests had been relatively small in recent months, amid fears of retaliation.

Assad attended holiday prayers in Al-Afram Mosque in the Al-Muhajireen district of Damascus, according to state-run Syrian media, in an apparent attempt to project business as usual. The embattled president was shown briefly on TV, sitting on the mosque floor and praying. He later was seen smiling and shaking hands with worshippers.

Security tight around capital

Security was tight around the capital, and police erected additional checkpoints on main roads. On side streets, people prayed or protested freely, said al-Shami, the Damascus activist.

"It seems there is an attempt by both sides to abide by this truce, at least in Damascus," he said, adding that "unfortunately [it] will not last."

Brahimi's holiday truce is less ambitious than a ceasefire plan proposed in April by his predecessor, Kofi Annan. The former UN chief had sought an opened-ended truce that was to pave the way for negotiations on the terms of a peaceful transition.

After an initial drop in violence, the April ceasefire disintegrated, and there appears to be widespread skepticism about the current attempt to make a truce stick.

Neither side has an incentive to lay down arms, since diplomatic options at home and abroad appear blocked.

The international community is divided over Syria and largely paralyzed, with Russia, Iran and China shielding Assad from harsher sanctions. In Syria, the lack of trust and common ground between Assad and his opponents prevents negotiations on the country's future.

Assad has dug in, dismissing his opponents as foreign-backed terrorists. Opposition leaders have denounced his offers of political reform as a ploy.

Analyst Shadi Hamid of the Brookings Institution said the truce is unlikely to change the trajectory of the Syrian conflict.

"It's a slow slog," he said. "Each day, if we take the longer view, is worse because we are further away from any kind of resolution."