BEIRUT // Scores of people were killed in recent days in the city of Hama, according to activists who blamed the deaths on forces loyal to the president Bashar Al Assad.
Opposition groups contended that more than 100 people were killed by regime forces.
However, Syrian state media yesterday gave a conflicting account yesterday, blaming "terrorists" for setting off an explosion that killed 16 people in Hama on Wednesday. Activists say 68 people died in the explosion and that Syrian shelling caused the fatalities.
The Syrian National Council (SNC), the main opposition group, said yesterday that regime forces were responsible for the deaths.
"We are calling for an emergency meeting of the UN Security Council so that it can issue a resolution to protect civilians in Syria," the SNC said in a statement.
"Hama in recent days, and following a visit by UN observers, witnessed a series of crimes ... that left more than 100 people dead and hundreds wounded because of heavy shelling."
The SNC said government forces had carried out "summary executions, raids [and] arrests" in Hama and that many residents had fled.
The Local Coordination Committees (LCC), a network of Syrian activists that monitors events on the ground, reported that 16 children were among those killed by government shelling in Hama on Wednesday alone.
Since the uprising against the Al Assad regime began in March last year, the government has blamed the violence on "armed terrorist groups" and said more than 3,000 members of the security forces have been killed.
The latest UN estimates placed the number of people killed in the 13-month crisis at more than 9,000.
The latest wave of violence came as UN military observers were monitoring the ceasefire that went into effect on April 12. While overall violence appears to have dropped, there were still daily reports of casualties and fighting on both sides.
The LCC reported yesterday that it had documented 462 people killed since the start of the observer mission.
There are believed to be 15 observers now on the ground in Syria, a team that eventually will grow to 300. The French foreign minister Alain Juppe predicted that the entire team should be on the ground within two weeks.
Two monitors were reportedly stationed in Hama. Under the plan to end the current crisis - put together by the UN-Arab League special envoy Kofi Annan - government troops were supposed to withdraw from population centres.
Speaking on Tuesday, Mr Annan said the Al Assad regime had failed to meet all of its commitments, adding that the situation was still "unacceptable".
France has said that if government forces were not redeployed from civilian areas, it would call for a UN Security Council resolution to authorise measures including the use of military force. However, many world powers have opposed military intervention.
Meanwhile, Russia yesterday accused Syrian rebels of carrying out Al Qaeda-style terrorist attacks.
"Opposition groups have essentially reverted to waging wide-scale terror in the region," said the Russian foreign ministry spokesman Alexander Lukashevich.
The LCC reported at least 13 people dead yesterday. Five were killed in the town of Deir Ezzor, the group said, and four in Aleppo. Gunfire and shelling was reported in Homs and tanks entered the city of Douma.
These reports could not be independently verified.
* Additional reports by Agence France-Presse, Reuters and the Associated Press