BEIRUT -- Syrian rebels on Thursday bombarded a military air base in Aleppo using a tank captured from government troops as activists reported the regime has launched new raids against opposition fighters near the capital Damascus, killing dozens.

It was one of the first indications the rebels are starting to deploy the heavy weapons they've managed to capture in the past weeks from the Syrian army. The Syrian Observatory for Human Rights said the rebel-seized tank shelled the Menagh military airport outside Aleppo, which the regime has used to launch attacks on rebel positions in the surrounding area.

The incident represents an escalation in the 17-month-old uprising in which an estimated 19,000 have died. Since the beginning, rebel forces have suffered from the huge disparity in armaments with Syria's well-armed military that also has fighter jets and helicopter gunships at its disposal.

Rebel forces in northern Syria attacked the country's largest city of Aleppo two weeks ago and have captured several neighbourhoods, mostly lower income areas on the periphery, which they have since held despite ground and air assaults by the government.

Residents reported Thursday that Internet and mobile phones were barely working since the night before, which has raised fears of an imminent government onslaught on Aleppo. But by early afternoon Thursday, there were only the daily, low level clashes around the rebel bastion of Salaheddine and shelling, a resident going by the name of Abu Adel told The Associated Press. Communications also began to work again by the end of the day.

With its proximity to rebel-friendly Turkey just to the north, Aleppo has enormous strategic importance to the opposition and if the rebels were able to capture and hold it, the city could form the kernel of a wider rebel-controlled zone.

"If Aleppo falls, then automatically we are going to establish headquarters at the presidential palace," said Syrian opposition leader Burhan Ghalioun, late Wednesday in Paris. The comments could be seen as overconfident, given that the regime still wields considerable power.

"Nothing more would stand in the way of the Free Syrian Army. Hama and Homs, to the outskirts of Damascus, have in large part been liberated."

The Syrian army, however, still has many more tanks and armoured vehicles than the rebels and there was no indication that Thursday's attack on the air base was particularly effective. Later, a nearby village was shelled by government forces out of that same air base.

There was also heavy shelling earlier in the day around the town of Azaz on the Turkish border, which has been in rebel hands for weeks along with a checkpoint crossing in the area, making it easier to deliver rebel weapons and supplies to the Aleppo battle. It would be a huge blow to the opposition if the government retook the crossing.

In the capital Damascus, the regime on Thursday announced a string of raids against rebels in neighbourhoods on the southern edge of the city the night before, killing and arresting "a number of terrorists," as the government refers to rebels.

Operations also took place in the well-to-do Muhajireen district on Thursday close to the presidential palace in Damascus. Activist Abu Qais, based in the Syrian capital, said 20 people were arrested.

Also on Thursday, the regime bombarded the southern suburb of Tadamon with artillery and mortars, sending plumes of smoke up into the sky, according to the Observatory. People in downtown Damascus confirmed hearing explosions coming from that direction and seeing smoke.

A bold rebel assault on Damascus was crushed two weeks ago in fierce fighting, but the latest raids show that pockets of resistance remain in the capital and the surrounding countryside.

Abu Qais said that at least 20 people were killed by raids in the Yalda suburb on Wednesday night, in the south, while the Observatory reported that 47 people had been killed in the Jdaidat Artouz neighbourhood to the southwest. Videos posted by activists show piles of bloody corpses, many with visible bullet holes. The videos could not be independently authenticated.

There has been a growing chorus of international condemnation of Syria's handling of the uprising and a vote is set for Friday in the UN General Assembly on a resolution drafted by Arab League countries.

The draft had to be softened, however, because of resistance from Brazil, Russia, India and China, finally dropping its call for Assad to step down and for sanctions on Syria.

While the 193-member General Assembly has no legal mechanism for enforcing a resolution, an overwhelming vote can carry moral and symbolic power.

The UN World Food Program, meanwhile, sounded the alarm Thursday over the humanitarian situation in Syria with close to 3 million people needing food and livestock assistance in the next 12 months -- more than 10 per cent of the country's population of 22 million.

The study carried out by the WFP as well as the Syrian Agricultural Ministry said the country's agricultural sector has lost $1.8 billion this year from damaged crops and livestock. It's not just the fighting that has kept farmers from their harvest but also shortages in fuel, electricity and labour to work the farms.

The statement warned that the country's poorest would be the hardest hit.