"A boy and a girl were killed by regime forces' shelling in the (rebel-held) town of Maaret al-Numan," the Syrian Observatory for Human Rights said.

Troops also bombarded the besieged city of Rastan, in the central province of Homs, the Britain-based watchdog added.

Children across the Muslim world were set to receive new clothes and gifts for Eid but in Syria, there was no respite from the bloodshed which the Observarory says has killed more than 23,000 people since March last year.

"This is how we celebrate Eid!" chanted a crowd of protesters who took to the streets of Kafr Zeita, in the central province of Hama, according to amateur video posted on YouTube by activists.

At the protest, children and adults held up Syrian independence flags and chanted slogans against President Bashar al-Assad.

Elsewhere, clashes raged in the Saif al-Dawla and Izaa districts of the northern city of Aleppo, a key battleground of the conflict since rebels seized large swathes from July 20.

At least 137 people were killed across Syria on Saturday 63 civilians, 31 rebel fighters and 43 soldiers, the Observatory said.