Syrian fighter jets blasted the rebel-held town of Maaret al-Numan on Thursday, killing at least 44 people, AFP reported.
Rescuers said bombs destroyed two residential buildings and a mosque, where many women and children were taking refuge, in the strategic northwestern town, which was captured by rebels on October 9 in a push to create a buffer zone along the Turkish border.
"We have recovered 44 corpses from under the rubble," one worker told an AFP correspondent at the scene.
In a makeshift field hospital, the correspondent saw at least 32 bodies wrapped in white sheets, including six children and many mutilated corpses, as well as plastic bags marked "body parts."
The correspondent said one child was decapitated while the body of a second, still on his bicycle, was pulled from the rubble.
Several fighter jets flew over Maaret al-Numan and the surrounding area throughout Thursday morning, reported AFP.
They made short dives to drop at least 10 bombs on the town and its eastern outskirts, near the besieged Wadi Deif army base which came under heavy bombardment by the rebels.
In early evening, the rebels launched what they said was a "final assault" on the base, which is a key depot for tanks and fuel supplies.
Hundreds of fighters attacked the base, a frontline AFP correspondent reported. Three tanks were destroyed and at least six soldiers surrendered, rebel officers said.
Meanwhile, in the capital Damascus, a suicide bomber on a motorcycle blew himself up just 300 meters from the interior ministry without causing any casualties, a security source said.
The bombing came on the eve of UN envoy Lakhdar Brahimi's arrival in Damascus to press his call for a ceasefire during the four-day Eid al-Adha Muslim holiday starting on October 26.
Speaking in neighbouring Jordan, Brahimi said he hoped that such a temporary ceasefire could form the basis for a longer lasting truce, warning that the alternative would be disastrous for the whole region.
"If the ceasefire is implemented, we can build on it and make it a real truce as well as the start of a political process that would help the Syrians solve their problems and rebuild their country," Brahimi said in Amman.
"If the Syrian crisis continues, it will not remain inside Syria. It will affect the entire region," he added, according to AFP.
The Algerian diplomat's visit to Syria for talks with Foreign Minister Walid Muallem on Saturday will be his last stop on a tour of countries that play influential roles in the crisis -- Egypt, Turkey, Saudi Arabia, Iran, Iraq, Lebanon and Jordan.
The envoy will also meet with President Bashar al-Assad "very, very soon, but not on Saturday," Brahimi's spokesman, Ahmad Fawzi, told AFP.
Asked whether any optimism was warranted over the Damascus talks, foreign ministry spokesman Jihad Maqdisi said: "Let's see what Brahimi has to say."
Damascus said it is ready to discuss with Brahimi his proposal but wanted assurances that countries with influence on the rebels would pressure them to reciprocate.
The exiled opposition said it would welcome any ceasefire but insisted the ball is in the government's court to halt its daily bombardments.