An expected US-led strike on Syria has not only put government forces on alert, it has also alarmed Islamist rebels - who worry they too are targets.
Twelve people were killed when an explosion rocked a government-held district of the disputed Syrian city of Aleppo, a monitoring group said.
Rebel forces have attacked Damascus while Turkey deployed anti-aircraft rocket launchers to the Syrian border, building pressure on Bashar al-Assad.
UN monitors say the smell of burnt flesh hung in the air and body parts lay scattered around the deserted Syrian hamlet of Mazraat al-Qubeir.
Syria has told Arab League envoy Kofi Annan that it has begun pulling troops in line with a peace plan accepted by President Bashar al-Assad.
The Syrian government kept up its onslaught on Homs and other towns, with at least 100 killed according to human rights campaigners.
Syria will hold a referendum on a draft Constitution on February 26 that limits the presidency to two seven-year terms and allows multiple parties.
Syrian government forces have attacked President Bashar al-Assad opponents on several fronts, sending residents fleeing from a town near the capital.
Syrian forces have bombarded districts of Homs and struck other cities after Arab states pledged support for the opposition battling Bashar al-Assad.
Frustrated with the Arab League's lack of progress, the head of the Free Syrian Army has threatened to step up attacks on Bashar al-Assad's forces.