Syrian regime warplanes have dropped cluster bombs in sorties against rebels in the northwestern town of Maaret al-Numan, the insurgents told AFP on Friday.
The rebels showed an AFP correspondent in the battleground Idlib province town debris from one such cluster bomb and dozens of other bomblets that failed to explode on impact.
On Sunday, Human Rights Watch issued a statement accusing the Syrian air force of using cluster bombs against the rebels and in populated areas across the strife-torn country.
The Syrian army denied the allegations, saying it did not possess such weapons.
The claim came as warplanes pounded the key rebel-hold town for a second straight day on Friday, hours before peace envoy Lakhdar Brahimi flies in to Damascus to press for a ceasefire.
Brahimi is aiming to secure a truce during the four-day Muslim feast of Eid al-Adha from October 26, hoping it will bring a longer halt to the bloodletting in the 19-month conflict that has already killed more than 34,000 people.
A wounded Syrian boy is carried to the hospital following an airstrike by Syrian government forces in Maaret al-Numaan on October 18. Warplanes pounded the key rebel-hold town in Syria for a second straight day on Friday, hours before peace envoy Lakhdar Brahimi flies in to Damascus to press for a ceasefire.
Violence has persisted on the ground, however, with loyalists of President Bashar al-Assad and rebels locked in an all-out battle for the town of Maaret al-Numan on the highway linking Syria's two biggest cities.
Assad's forces, who hold supremacy in the air, battered the northwestern town at dawn, a day after strikes on a residential area killed dozens, nearly half of them children, rescuers told an AFP reporter at the scene.
The raids are aimed at trying to regain control of the highway to resupply units under fire in the northern metropolis Aleppo for the past three months, and assist 250 troops besieged in their Wadi Deif base.
Fighter jets overflew at high altitude before nosediving to make four to five hits on targets in the town's outskirts, as helicopter gunships buzzed the area, the correspondent said.
The Syrian Observatory for Human Rights said targets included rebels camped near Wadi Deif, which is also a major storage facility for heavy armour and fuel.
"Military aircraft dropped bombs that targeted rebels camped near (the base at) Wadi Deif," concentrating their firepower on the villages of Talmans and Maashemsha, it said.
The rebels say they have launched a "final assault" on Wadi Deif, which is surrounded by around 2,500 insurgents, says the Observatory, adding at least six soldiers have been killed so far.
They responded to the air strikes by opening fire from heavy machineguns mounted on four-wheel drive vehicles.
"It doesn't matter if we die. We must shoot down these planes," said one of the fighters manning a machinegun.
Rockets also rained down on Maaret al-Numan at a interval of 15-20 minutes, some of them fired by soldiers holed up inside Wadi Deif.
On Thursday, warplanes targeting residential areas of Maaret al-Numan killed at least 49 people, among them 23 children, rescuers said.
The strikes destroyed two housing complexes and a mosque, where many women and children had taken refuge, with bodies still trapped under the rubble of the mosque, medics and rescuers said.
Among those killed was a nine-month-old baby.
Chubby feet resting on bicycle pedals and a decapitated head were all that was left of a boy caught unaware by the blitz as he played outside his home.
Violence across Syria killed 195 people on Thursday -- 89 civilians, 61 soldiers and 45 rebels, said the Observatory, which relies on a network of activists, medics and lawyers for its information.
Syrian men react following an airstrike by Syrian government forces in Maaret al-Numan on October 18, 2012. Warplanes pounded the key rebel-hold town in Syria for a second straight day on Friday, hours before peace envoy Lakhdar Brahimi flies in to Damascus to press for a ceasefire.
The bloodshed mounted as Brahimi again appealed for both sides to lay down their arms in a goodwill gesture to mark the Eid al-Adha holiday, saying such move could pave the way for a long-term ceasefire.
"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.
But he also warned: "If the Syrian crisis continues, it will not remain inside Syria. It will affect the entire region."
Brahimi is due to hold talks with Foreign Minister Walid Muallem in Damascus on Saturday, according to the foreign ministry, and his spokesman said he will also meet President Assad at a later date.
His visit to Syria will be the last stop on a tour of countries that play influential roles in the crisis -- Egypt, Turkey, Saudi Arabia, Iran, Iraq, Lebanon and Jordan.
But doubts loom large over his ability to halt the bloodshed, even temporarily.
Damascus said it was ready to discuss the ceasefire proposal with the veteran troubleshooter, 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 it was for the government to halt its daily bombardments.