Activists say at least 217 people have been killed in Syria in shelling by government forces in the rebel city of Homs.
It comes as the United Nations Security Council prepares to vote on a draft resolution that is likely to back an Arab call for President Bashar al-Assad to give up power.
Russia has said it will veto any resolution calling for Mr Assad to stand down.
The Syrian Observatory For Human Rights cited witnesses as saying that hundreds were wounded in the latest outburst of fighting in Syria's 11-month uprising against Mr Assad.
The British-based group says Syrian forces are shelling the district with mortars from several locations, and some buildings are on fire.
It is not possible to verify activist or state media reports as Syria restricts access for independent media.
Syrian embassies attacked
The BBC reports activists have attacked Syrian embassies around the world.
About 20 protesters forced their way into the Syrian embassy in Berlin late on Friday and damaged offices, police said.
German TV showed a Syrian resistance flag hanging from one of the windows and graffiti sprayed on the outside of the building.
About 150 demonstrators also gathered outside the Syrian embassy in London early on Saturday and five people were arrested after entering the building.
In Cairo, protesters stormed the embassy building, smashing furniture and setting fire to parts of the building.
UN Security Council to vote on draft resolution
At the United Nations, the Security Council was due to meet later in the day to vote on a European-Arab draft resolution endorsing an Arab League plan calling for Assad to resign.
Diplomats said it was unclear if Russia, which has opposed significant council action on Syria, would vote in favour, abstain or veto the resolution.
Russia has balked at any language that would open to door to "regime change" in Syria, its most important Middle East ally.
A vote may not be imminent and further revisions could follow.