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 early on Thursday if government forces begin pulling back from towns 48 hours earlier in line with UN-Arab League envoy Kofi Annan's peace plan.
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 showed scenes of carnage said to be the aftermath of the shelling. Mangled limbs and body parts in blankets were being loaded on a pick-up truck. A second video showed 13 men who appeared to have been tied up and executed.
No comment was immediately available from Syrian officials. The videos could not be independently verified. The government has placed tight restrictions on media access in Syria.
The Syrian Observatory for Human Rights said at least 74 civilians had been killed, including 40 in an army attack on al-Latmana, in Hama province, that began on Friday. The rebel Free Syrian Army lost 15 men in the battle, it said, and 17 members of the security forces were killed across the country.
In an activist video from al-Latmana, mourners held aloft the limp corpse of a child. A row of bodies lay on the ground.
The Observatory report said 12 were killed by shelling as the army swept through villages in Idlib province.
A rocket hit a bus travelling from Lebanon to Syria at Jousa just inside Syria, a Lebanese security source said. Witnesses said six Syrians were killed. Lebanese medics confirmed two dead and nine wounded. It was not clear who had fired the rocket.
Rebels trying to oust President Bashar al-Assad attacked army posts north of Aleppo before dawn, killing an officer and two men, and assaulted a helicopter base, activists said.
Syrian commandos shot dead three rebels in an overnight raid on a "terrorist den", Syria's state news SANA agency reported.
Country towns north of Aleppo have endured days of clashes and bombardment, prompting 3,000 civilians to flee over the Turkish border on Friday alone - about 10 times the daily number before Assad accepted Annan's plan 10 days ago.
Turkish Prime Minister Tayyip Erdogan said on Saturday the number of refugees entering Turkey was rising. Ankara fears an all-out war in Syria would unleash a flood of refugees.
"At the moment we have 24,000 Syrians who have entered Turkey. Of course this number is rising," Erdogan told reporters before departing on a trip to China.
"We are taking measures for this, though we will not close the gates. The United Nations, however, has to toughen its stance," he said. "In particular Kofi Annan has to hold firm. He announced a deadline of April 10. I believe that he should monitor the situation very closely."
