Mortar fire killed 105 people and left hundreds more injured in a "massacre" in the central Syrian city of Homs overnight Friday, the Syrian Observatory for Human Rights said.
The rights group said the mortar fire had hit the Al Khalidiya district of Homs, which has become a flashpoint of the 10-month revolt against the regime of President Bashar al-Assad.
"It's a real massacre," the observatory's director Rami Abderrahman told AFP, calling for the "immediate intervention" of the Arab League to end the killing.
The Al Jazeera and Al-Arabiya television channels showed images of dozens of bodies on the ground.
The Syrian Observatory also reported that two civilians were killed in the Damascus suburb of Rastan late Friday, while eight army deserters were shot dead in various regions of Syria.
The violence broke out after thousands of people across Syria defied the government crackdown to mark the 30th anniversary of a notorious 1982 massacre in the central city of Hama that killed thousands.
News of the latest deaths came as a diplomat in New York said members of the UN Security Council would meet Saturday morning for a vote on a resolution condemning the violent repression in Syria.
The text is the same as a draft resolution sent to the council's 15 members on Thursday.
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It highlights the UN body's support for an Arab League plan for a democratic transition while leaving out explicit references to calls for Assad to step down, the diplomat said Friday.
The Homs violence ended an already bloody day in Syria which, by the Syrian rights group's count, left 150 people dead.
At least 35 people were reported killed across the country in other incidents on Friday, among them 16 civilians, the Syrian Observatory for Human Rights said.
The Britain-based group said 14 soldiers were also killed in clashes with the rebel Free Syrian Army (FSA) and that five army deserters also lost their lives.
In addition, one person died of wounds sustained on Thursday, and the bodies of three other people were either found or returned to their families.
Amid growing concern that Syria is sliding into all-out civil war, an officer with the FSA claimed the regular army "is in a pitiful state and getting close to collapsing."
Major Maher Nouaimi, based in Turkey, told AFP by telephone that "even though the army has huge military capabilities, soldiers no longer have the will to fight or are ready to do so."
He said there was growing discontent among officers and the rank and file against commanders, who are largely drawn from Assad's Alawite community, an offshoot of Shiite Islam.
Most conscripts in the military are from Syria's majority Sunni Muslim community.