Explosions have rocked several army ammunition depots in the western province of Latakia, according to the Syrian Observatory for Human Rights, which relies on a network of activists and officials on the ground for its information.
Observatory director Rami Abdel Rahman said there were reports of deaths and injuries in the blasts on Friday.
There were indications that the blasts were caused by rocket fire targeting the depots, but that there was uncertainty over who was behind the attack, Abdel Rahman said.
Elsewhere, the air force carried out at least three raids on besieged sectors of the central city of Homs, where troops have been battling to roll back rebel forces, the organisation said.
The observatory reported heavy shelling on the Khaldiyeh district and the Old City of Homs, adding that regime forces backed by the National Defence Force militia and members of Lebanon's Shia group Hezbollah were fighting rebels on the outskirts of Khaldiyeh.
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The group said eight members of government forces were killed in fighting on Thursday in the two neighbourhoods of Homs, which have been under siege by the army for more than a year.
At least 106 people were killed in fighting throughout Syria on Thursday, including 38 civilians, 46 rebels and 22 soldiers, according to the observatory.
Homs, dubbed the "capital of the revolution", has paid an enormous human and material price for the uprising against the government of President Bashar al-Assad that began in March 2011 and has since evolved into a fully-fledged civil war.
Syria's main opposition bloc has urged the international community to take action to protect civilians in the embattled city.
The Syrian National Coalition on Friday appealed to the UN and Western countries that have supported the opposition "to intervene immediately" and provide food and medicine to the besieged, rebel-held areas of the central city.
The appeal comes as opposition figures are meeting in Turkey to elect a new leadership.