THE Syrian military stepped up its campaign to drive rebel fighters out of Aleppo yesterday, firing artillery and mortars while a fighter jet flew over a district the army said it had retaken the day before.

However, opposition activists denied government forces had entered the Salaheddine district, which lies in the southwest of Syria' s biggest city and straddles the most obvious route for Syrian troop reinforcements from the south.

Hospitals and makeshift clinics in rebel-held eastern neighbourhoods were filling up with casualties from a week of fighting in Aleppo, a commercial hub that had previously stayed out of a 16-month-old revolt against President Bashar al-Assad.

"Some days we get around 30, 40 people, not including the bodies," said a young medic in one clinic. "A few days ago we got 30 injured and maybe 20 corpses, but half of those bodies were ripped to pieces. We can't figure out who they are."

The Syrian Observatory for Human Rights said 40 people, including 30 civilians, were killed in Syria yesterday.

Outgunned rebel fighters, patrolling in flat-bed trucks flying green, white and black "independence" flags, said they were holding out in Salaheddine despite a battering by the army's heavy weapons and helicopter gunships.

The army's assault on Salaheddine echoed its tactics in Damascus earlier this month when it used its overwhelming firepower to mop up rebel fighters district by district.

Mr Assad's forces are determined not to let go of Aleppo, where defeat would be a serious strategic and psychological blow.

The new head of the United Nations observer mission in Syria said he had seen heavy shelling of Homs during a field visit on Sunday, as well as major damage in Rastan.

"During my visit to Homs, I was personally able to witness heavy shelling from artillery and mortars ongoing in the neighbourhoods of the city," Lt-Gen Babacar Gaye said. "Rastan was heavily damaged by an intensive shelling campaign and fierce fighting."

Military experts believe the rebels are too lightly armed and poorly commanded to overcome the army, whose artillery pounds the city at will and whose gunships control the skies.

Reuters, Sapa-AFP