Syrian troops have pounded opposition areas killing 74 civilians, activists said, in an offensive days before a UN-backed ceasefire was due to be implemented.
At least 15 rebels and 17 security force members were also killed, raising the death toll in violence to over 100.
Each side has accused the other of intensifying assaults in the run-up to the truce due to take effect on 12 April.
The military shelled Deir Baalba district in Homs, killing four people, the grassroots Local Coordination Committees opposition group said. Thirteen men were also found killed in cold blood in the same area, it said.
Amateur activist video, which could not be independently verified, showed scenes of carnage said to be the aftermath of the shelling.
A second video showed 13 men who appeared to have been tied up and executed.
No comment was immediately available from Syrian officials.
The Syrian leader, President Bashar al-Assad, is fighting a popular uprising, which he blames on foreign-backed "terrorists", that has spawned an armed insurgency in response to violent repression of protests.
While many in Syria's Sunni Muslim majority back the revolt, especially in provincial areas, Mr Assad retains support from his own minority Alawite sect and other minorities fearful that his overthrow would lead to civil war or Islamist rule.
A ceasefire plan put forward by former UN head Kofi Annan requires President Assad to "begin pullback of military concentrations in and around population centres" by 10 April.
Syria has said the plan does not apply to armed police, who have played a significant role in battling the uprising in which security forces have killed more than 9,000 people, according to UN estimate. Syria says its opponents have killed more than 2,500 troops and police since the unrest began in March 2011.
Rebel Free Syrian Army commander Colonel Riad al-Asaad said his men would cease fire, provided "the regime ... withdraws from the cities and returns to its original barracks".
Mr Annan's plan does not stipulate a complete army withdrawal to barracks, nor does it mention police.
Satellite pictures published by US ambassador Robert Ford showed Syrian artillery and tanks still close to communities.