ALEPPO, Syria, July 30 (Reuters) - Artillery and mortar fire reverberated across Aleppo early on Monday and a military helicopter clattered towards a district that the Syrian army said it had recaptured from rebels in battles for control of Syria's biggest city.

Hospitals and makeshift clinics in rebel-held areas in the east of the city were filling up with casualties from a week of fighting in Aleppo, an 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 opposition Syrian Observatory for Human Rights said 18 people were killed in the Aleppo area on Sunday out of more than 150 people, two thirds of them civilians, slain across Syria.

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

However, the government said it had pushed them out of Salaheddine, the focus of fighting in the southwest of the city.

"Complete control of Salaheddine has been (won back) from those mercenary gunmen," an unidentified military officer told Syrian state television late on Sunday. "In a few days safety and security will return to the city of Aleppo."

EMPTY STREETS

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.

Assad's forces are determined not to let go of Aleppo, where defeat would be a serious strategic and psychological blow. But 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 journalists in Aleppo were not able to approach Salaheddine after nightfall on Sunday to verify who controlled it. The Syrian Observatory said fighting was still in progress.