Syrian jets bombed parts of Damascus today in what residents said were the capital's fiercest air raids yet, at the end of what was supposed to be a four-day truce.

"More than 100 buildings have been destroyed, some levelled to the ground," said opposition activist Moaz al-Shami. "Whole neighbourhoods are deserted."

Each side in the 19-month-old conflict between President Bashar al-Assad and rebels blamed the other for breaking the truce proposed by peace envoy Lakhdar Brahimi to mark a Muslim holiday.

Two car bombs rocked the capital today, state media reported.

"I am deeply disappointed that the parties failed to respect the call to suspend fighting," UN Secretary-General Ban Ki-moon said.

"This crisis cannot be solved with more weapons and bloodshed ... the guns must fall silent."

Although the military and several rebel groups accepted the plan to stop shooting over Eid al-Adha, which ends today, 500 people have been killed since Friday, according to the Syrian Observatory for Human Rights, an opposition organisation.

Damascus residents said today's air raids were the heaviest since jets and helicopters first bombarded pro-opposition parts of the capital in August.

State media said "armed terrorist groups" had broken the truce over the four days in the cities of Aleppo, Homs and Deir al-Zor and had detonated two car bombs in the capital today.

One killed ten people, including women and children, near a bakery in Jaramana, a district controlled by forces loyal to Mr Assad.

The other was in Hajar al-Aswad, a neighbourhood where rebels are based.