Syrian forces bombarded parts of the central city of Homs on Thursday for the 20th day, opposition activists said, in an attempt to crush rebel fighters, dpa reported.
The European Union was preparing a new round of sanctions against the regime of President Bashar al-Assad, and representatives from more than 60 countries and multilateral organizations were to meet at the Friends of Syria conference in Tunis on Friday.
Activists said government forces killed 47 people as international pressure increased on the regime to stop the violence.
Thirteen people were killed in attacks on the Baba Amr neighbourhood in Homs, activist Omar Idlibi told dpa. Rebels and civilians in Baba Amr fear a ground invasion of the area, which they say is besieged by tanks and armoured vehicles.
The British and French authorities are coordinating with the International Committee of the Red Cross (ICRC) to transfer three wounded Western journalists to Lebanon.
Edith Bouvier, a freelance reporter for French daily Le Figaro, Paris-based William Daniels and Sunday Times photographer Paul Conroy were injured in Baba Amr on Wednesday.
France has said it holds the Syrian government responsible for Wednesday's attack on a makeshift press centre and demanded to be given access to the victims, along with the ICRC.
Bouvier, who was badly wounded in the attack that killed two foreign journalists, issued a video plea Thursday to be evacuated to Lebanon for urgent treatment.
In the video posted online by opposition activists, Bouvier appears lying on a bed under a blanket. She relates how she was injured in the bombardments that killed US reporter Marie Colvin and French photographer Remi Ochlik.
"I have a broken leg from the femur, lengthwise and horizontally too. I need to be operated as quickly as possible," she said.
"The doctors here have treated us as well as they could but they can't perform surgery. So I need a ceasefire as quickly as possible and an ambulance or car in good enough shape to drive us to Lebanon," she added.
Lying in a bed, Conroy said in a separate video that he had suffered "three large wounds" to his leg, and was being looked after by Free Syrian Army medics.
The journalists were smuggled into Syria since reporting by foreign media and humanitarian organizations is severely restricted.
British Foreign Secretary William Hague said the international community would tighten the "diplomatic and economic stranglehold" on Syria to force al-Assad to step down and end the bloodshed.
"Time is against the Assad regime," Hague said in London on the sidelines of a conference on Somalia.
Hague said the Friends of Syria conference would seek to bolster sanctions against the al-Assad regime.
The EU said it would approve new sanctions against Syria on Monday. The measures will target the Syrian central bank, seven government ministers, cargo flights, and trade in precious metals, an official said on condition of anonymity.
The Syrian government has continued its crackdown despite sanctions and a UN General Assembly this month calling on al-Assad to step down and demanding an end to the violence.
Activists said 14 people near the north-eastern city of Deir al-Zour, including two children, were among those killed Thursday by government forces.
Seventeen people, including 12 from one family, were killed in government attacks on areas in the central province of Hama.
Three others were killed in Aleppo, Syria's second-largest city, where security forces fired on a mass protest held in support of Homs, activists said.