An explosion destroyed a building in Syria's central city of Hama, killing dozens and wounding many more.
The opposition Local Co-ordination Committees (LCC) said security forces fired a rocket at the building in the Mashaa Attayar area on Wednesday. It put the death toll at 54, with 70 more wounded.
Activists said among the dead were 13 children and 16 women, with more bodies still under the rubble.
Footage on YouTube of the blast showed a crowd of men pulling out the bloodied body of a young girl.
Another video shows the collapsed remains of the building, as ash-covered men dig through piles of masonry looking for bodies amid the cries of onlookers.
An activist who asked not to be named said the blast may have been an explosion from inside the building.
Hama, a hotbed of revolt in the year-long uprising against President Bashar al-Assad's rule, has a small team of UN observers, who are preparing the way for a larger UN mission which will monitor the peace plan brokered by UN-Arab League envoy Kofi Annan two weeks ago.
Two days ago, activists said Syrian forces shelled another district of Hama, killing at least 20 people and wounding more than 60.
There was no immediate comment from Syrian authorities who say they are committed to international mediator Kofi Annan's April 12 ceasefire agreement, but reserve the right to respond to what they say are continued attacks by "fighters groups".
Hama is a particularly sensitive site for the opposition. Assad's father, Hafez al-Assad, crushed an armed uprising in Hama 30 years ago, killing many thousands of people and flattening parts of Hama's old city.
Meanwhile, the French foreign minister has said the UN Security Council should consider military action in Syria if an international peace plan fails to stop the violence.
Alain Juppe also demanded that 300 UN observers authorized to go to Syria be deployed within 15 days. He said Paris would consider peace envoy Kofi Annan's scheduled report on May 5 as a deadline for Damascus to comply with the plan.
"We think this mediation should be given a chance, on the condition that the deployment of the observer mission happens quickly,'' Juppe said after a meeting with Syrian dissidents at his ministry.
Juppe said that Annan's report on May 5 on the state of the UN-backed ceasefire will be "a moment of truth: Either this mediation is working, or it isn't''.
Juppe said France has been discussing with other world powers the prospect of invoking Chapter 7 of the UN Charter, which allows for action that could be militarily enforceable.
The LCC also said Syrian forces launched a second day of attacks on the Damascus suburb of Douma, despite recent visits to the town by UN ceasefire monitors.
Amateur video released from Douma showed rubble-filled streets with scorched storefronts and burned out vehicles after the reported shelling attacks.
In the northwestern province of Idlib, activists said four civilians were killed as security forces shot on a bus at a checkpoint on the main road from Aleppo to Damascus.
PHOTO CAPTION
An explosion tore through a building in Hama, leaving at least 12 people dead and wounding dozens according the Syrian Observatory for Human Rights.
Aljazeera