Syria's prime minister has been sacked, state television reported on Monday, as government forces appeared to prepare a ground assault to clear battered rebels from Aleppo, the country’s biggest city.

President Bashar Al Assad appointed Riyad Hijab, a former agriculture minister, as prime minister only in June following a parliamentary election which authorities said was a step towards political reform but which opponents dismissed as a sham.

A bomb blast hit the Damascus headquarters of Syria’s state broadcaster on Monday as troops backed by fighter jets kept up an offensive against the last rebel bastion in the capital.

The bomb exploded on the third floor of the state television and radio building, state TV said. However, while the rebels may have struck a symbolic blow in their 17-month-old uprising against Assad, Information Minister Omran Zoabi said none of the injuries was serious, and state TV continued broadcasting.

Rebels in districts of Aleppo visited by Reuters journalists seemed battered, overwhelmed and running low on ammunition after days of intense tank shelling and helicopter gunships strafing their positions with heavy machinegun fire.

Emboldened by an audacious bomb attack in Damascus that killed four of Assad’s top security officials last month, the rebels had tried to overrun the Damascus and Aleppo, the country’s commercial hub.

But the lightly armed rebels have been outgunned by the Syrian army’s superior weaponry. They were largely driven out of Damascus and are struggling to hold on to territorial gains made in Aleppo, a city of 2.5 million.

Paralysis in the UN Security Council over how to stop the bloodshed forced peace envoy Kofi Annan to resign last week, his ceasefire plan a distant memory.

On Monday, Syrian army tanks shelled alleyways in Aleppo where rebels sought cover a helicopter gunship fired heavy machinegun fire.

Snipers ran on rooftops targeting rebels, and one of them shot at a rebel car filled with bombs, setting the vehicle on fire. Women and children fled the city, some crammed in the back of pickup trucks, while others walked on foot, heading to relatively safer rural areas.

Aleppo Gateway

The main focus of fighting in Aleppo has been the Salaheddine district, a gateway into the city. One shell hit a building next to the Reuters reporting team, pouring rubble on to the street and sending billows of smoke and dust into the sky.

State television said Assad’s forces were “cleansing the terrorist filth” from the country, which has been sucked into an increasingly sectarian conflict that has killed about 18,000 people and could spill into neighbouring states.

The army appeared to be using a similar strategy in Aleppo to the one used in other cities where they subjected opposition districts to heavy bombardment for days, weakening the rebels before moving in on the ground, clearing district by district.

Syria’s two main cities had been relatively free of violence until last month when fighters poured into them, transforming the war. The government largely repelled the assault on Damascus but has had more difficulty recapturing Aleppo.

Rebel commanders say they anticipate a major Syrian army offensive in Aleppo and one fighter said they had already had to pull back from some streets after army snipers advanced on Saturday under cover of the fierce aerial and tank bombardment.

“The Syrian army is penetrating our lines,” said Mohammad Salifi, a 35-year-old former government employee. “So we were forced to strategically retreat until the shelling ends,” he said, adding the rebels were trying to push the army back again.

Late on Sunday rebels clashed with the army in Aleppo’s south-eastern Nayrab district, a fighter who called himself Abu Jumaa said. The army responded by shelling eastern districts. There were also clashes on the southern ring road, which could be a sign the army was preparing to surround the city.