Rebels have stepped up attacks on regime-held areas of Aleppo in the run-up to Tuesday presidential election, killing 54 in two days, a monitoring group said.
Syrian state television, meanwhile, reported that 10 people were killed Monday in a truck bomb attack in the central province of Homs where government troops have recently made advances.
The Syrian Observatory for Human Rights said four people were killed on Monday in rebel mortar and rocket fire on regime-held areas of Aleppo, taking the overall death toll since Saturday to 54.
Fifty people were killed on the weekend, said the Britain-based monitoring group.
"The escalation by rebels against regime-held areas is linked to (Tuesday's) presidential election" that is expected keep Assad in power, said Observatory director Rami Abdel Rahman.
The opposition and their Arab and Western backers have dismissed the election as a sham, while the rebel Free Syrian Army has called on Syrians to boycott the poll.
Assad, is facing two little known candidates, is expected to win a third, seven-year term in office in the election that will be held only in regime-controlled areas.
Once Syria's commercial capital, Aleppo has been divided between pro- and anti-regime areas since a major rebel offensive in July 2012.
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Some 2,000 civilians, including more than 500 children, have been killed in regime air strikes on rebel-held areas of Aleppo since January, many of them in barrel bomb attacks.
"Targeting civilians is a war crime and the fact that the regime uses barrel bombs to target civilians in rebel areas does not justify targeting civilians in regime areas," said Abdel Rahman.
State television said the truck bomb attack struck the village of Haraqi in the central province of Homs and was carried out by "terrorists".
Haraqi is a regime-held village and home to a majority of Alawites, the religious community from which Assad's clan hails.
On Sunday the Observatory reported that a family of Alawites, including an 102-year-old man, were killed in central Hama province by fighters of the Islamic State of Iraq and the Levant (ISIL).
The group is the most radical of jihadist movements fighting in Syria and has been accused of carrying out many atrocities.
The Observatory said among its latest actions ISIL kidnapped on Thursday more than 150 Kurdish high school students along the Aleppo-Minbej road in northern Syria.
The teenagers, boys and girls, were abducted as they were returning home from the city of Aleppo where they had sat their end of year exams. ISIL was once welcomed by rebels fighting to topple Assad, but gained their wrath because of their quest for hegemony and systematic abuses.
More than 162,000 people have been killed in Syria since the conflict there broke three years ago, according to the Observatory, while millions have been forced to flee their homes.