Syrian rebels launched a series of attacks on army positions on Sunday as regime air strikes hit opposition-held towns near Damascus after the failure of a Muslim holiday ceasefire, a watchdog said.
Rebels seized three military posts in the outer Damascus suburb of Douma and killed four soldiers at another checkpoint in the region, the Syrian Observatory for Human Rights said.
Regime warplanes hit targets in the towns of Irbin, Zamalka and Harasta, where the military has been trying for weeks to dislodge rebel forces, it said.
They also hit a building in the town of Bara in the northwestern province of Idlib, said the Observatory, killing a child, a woman and two men, and wounding several others.
The number of victims was expected to rise as more wounded were rescued from under the rubble, it added.
Southeast of Damascus, a car bomb ripped through the Sbeineh area, although there were no immediate reports of casualties.
The violence came after the failure of efforts to impose a four-day ceasefire in the battle-scarred country for Eid al-Adha, which started on Friday.
"If this is a truce, then what level of violence can we expect once Eid is over?" asked Observatory director Rami Abdel Rahman, who described the ceasefire as failed hours after it began.
At least 40 people were killed in violence nationwide on Sunday, according to a preliminary Observatory count: 17 civilians, 13 rebels and 10 regular troops.
In Aleppo, fighting erupted in several districts of the embattled northern city, as the army shelled two neighbourhoods including the ancient souks in the heart of Syria's commercial capital, it said.
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The souks, part of Aleppo's UNESCO-listed Old City district, were hit by a fire caused by fighting there in late September.
In Aleppo province, rebels freed some 120 Kurds taken hostage after clashes between Kurdish militia and anti-regime fighters, the Observatory said.
Abdel Rahman warned that scores of Kurds remain in captivity. "Half of those taken hostage on Friday have been released," he said.
Meanwhile, protests against the presence of armed groups broke out in the rebel-held town of Aazaz, near the Turkish border, the Observatory and activists said.
Armed groups who fight independently from the main rebel Free Syrian Army are believed to be holding scores of people captive in Aazaz, including Lebanese journalist Fida Itani, whose capture was reported on Saturday.
"People took to the streets in Aazaz to protest against armed groups inside the town and to denounce their intervention in civilian affairs," said Aazaz-based anti-regime activist Abu Mohammed.
"They also called for those being held captive without charge to be released."
In nearby Idlib province, the army tried to retake the town of Maaret al-Numan, which rebels seized on September 9, said the Observatory, adding that rebels destroyed a tank and killed three soldiers.
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 a regime dominated by Assad's minority Alawite sect, an offshoot of Shiite Islam.
The Britain-based watchdog relies on a countrywide network of activists, lawyers and medics in civilian and military hospitals in compiling its tolls.