Syrian forces have fired mortars and rockets, killing scores of people in the rebellious city of Homs, activists say.
It is the latest strike in a weeklong assault as President Bashar Assad's regime tries to crush increasingly militarised pockets of dissent.
During lulls in the onslaught, Syrians used loudspeakers to call for blood donations and medical supplies. "There is medicine in the pharmacies, but getting it to the field clinics is very difficult, they can't get the medicine to the wounded," Mohammed Saleh, a Syria-based activist, said by telephone.
As the violence grinds on, the international community is searching for new diplomatic approaches to stop the protracted bloodshed. The regime's crackdown on dissent has left it almost completely isolated internationally, but Assad is receiving political backing from Russia and China, which delivered a double veto over the weekend that blocked a UN resolution calling on him to leave power.
Sanctions are crippling the Syrian economy, but they have failed to stop military offensives that have led to an overall death toll of more than 5,400 people since March.
A senior Arab League official said it will discuss at a meeting on Sunday whether to recognise the opposition Syrian National Council as the legitimate representative of Syria and whether to allow it to open offices in Arab capitals.
Homs, Syria's third-largest city, has become the focus of both resistance and reprisal in the 11-month uprising as many areas have fallen under the control of increasingly bold army defectors who want to bring down the regime by force.
In the latest operation, which began on Saturday, government forces have unleashed a relentless offensive, shelling residential areas as they try to root out any resistance and retake control of the city of one million people. Hundreds are believed to have been killed in the heaviest bombardment the city has seen since the country's uprising began in March, activists said.
The Britain-based Syrian Observatory for Human Rights and the LCC were trying to compile numbers and names of those killed on Thursday. The Local Co-ordination Committees, an activist group, said an estimated 90 people were killed in Homs, but the death toll was impossible to independently verify. Activists also reported violence in Zabadani and Daraa.
UN Secretary-General Ban Ki-moon has said the head of the Arab League plans to send observers back into Syria and has raised the possibility of a joint mission with the United Nations.
www.arableagueonline.org(Arab League website)