Cluster bombs hit as Syria envoy arrives

At least 44 people have been killed as Syrian fighter jets blasted the town of Maaret al-Numan. (AAP)

At least 44 people have been killed as Syrian fighter jets blasted the town of Maaret al-Numan. (AAP)

Rebels and loyalists are locked in battle for the northwestern town of Maaret al-Numan on the highway linking Syria's two biggest cities.

Syrian jets hammered a rebel town on Friday on the second day of an assault in which the regime is accused of using cluster bombs, as peace envoy Lakhdar Brahimi arrived in Damascus to press for a truce.

Brahimi is bidding to secure a ceasefire during a four-day Muslim holiday from October 26, hoping it will bring a longer cessation in the 19-month conflict that has already killed more than 34,000 people.

Violence has persisted, however, with rebels and loyalists of President Bashar al-Assad locked in battle for the northwestern town of Maaret al-Numan on the highway linking Syria's two biggest cities, Damascus and Aleppo.

Assad's forces, who hold air supremacy, again battered the town a day after strikes on a residential area killed dozens, nearly half of them children, rescuers told an AFP reporter at the scene.

The military wants to regain control of the highway to resupply units under fire in Aleppo for the past three months, and assist 250 troops besieged in their Wadi Deif base.

Fighter jets overflew at high altitude before nosediving and striking targets on the town's outskirts, as helicopter gunships buzzed the area, the correspondent said.

The Syrian Observatory for Human Rights said the aircraft concentrated their firepower on rebel camps near Wadi Deif, also a major storage facility for armour and fuel.

Rebels showed AFP debris from cluster bombs which they accused the air force of dropping on residential areas, as well as dozens of other bomblets that failed to explode on impact.

The weapons bear the Cyrillic script on their tail fins, suggesting they could have been made in Russia, a key ally of Damascus.

Human Rights Watch has accused Syria of using cluster bombs, a charge denied by the military which insists it does not have any.

The observatory also reported cluster bombs were dropped last week on the town of Saraqeb north of Maaret al-Numan.

Syria has not ratified an international convention banning the weapon which can carry up to 650 submunitions.

Non-governmental groups say up to 40 per cent of the bomblets fail to explode and that 98 per cent of victims are civilians, including children who mistake them for toys.

The rebels say they have launched a "final assault" on Wadi Deif, which is reportedly surrounded by about 2500 insurgents.

They responded to the air strikes by opening fire from heavy machine guns mounted on pick-up trucks.

Clashes around the base dropped in intensity overnight, according to the insurgents.

"We are still laying siege to the base but we are waiting for fresh ammunition," one of the commanders, Raed Mandil, told AFP.

Fighter jets targeting residential areas in Maaret al-Numan on Thursday 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.

Brahimi was received at Damascus airport by Syria's deputy foreign minister, Faisal Muqdad, and was scheduled to meet Foreign Minister Walid Muallem on Saturday. He is expected to hold talks with al-Assad at a later date.

On Thursday, the UN-Arab League envoy again appealed for both sides to lay down their arms for Eid al-Adha, which marks the end of the annual pilgrimage to Mecca.

"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," he said in Amman.

"If the Syrian crisis continues, it will not remain inside Syria. It will affect the entire region."

But doubts loom large over Brahimi's ability to halt the bloodshed, even temporarily.

Damascus says it is ready to discuss the proposal with Brahimi. The opposition says it would welcome any truce but insists the regime must first halt its daily bombardments.

The conflict began in March 2011 with pro-reform protests inspired by the Arab Spring, but is now a civil war pitting mainly Sunni Muslim rebels against al-Assad's regime dominated by his minority Alawite sect, an offshoot of Shi'ite Islam.