American warplanes were backing Afghan forces against a major Taliban offensive in the south of the country even as the US military pressed on with a troop withdrawal, officials said yesterday. 

Fierce fighting has erupted in Helmand province since the weekend, when the US military formally began withdrawing its remaining troops.

They were supposed to have been pulled out by May 1 under a deal struck with the Taliban last year, but Washington pushed back the date to September 11 -- a move that has angered the insurgents.

"The heavy US air strikes against the Taliban positions stopped them from advancing towards Lashkar Gah," said Atiqullah, a local government official, referring to the provincial capital.

"The bombing was intense. I have never seen such bombardment in several years."

Attaullah Afghan, head of the Helmand provincial council, told AFP Taliban forces had made advances, but government forces had "retaken some of these areas".

A US defence official confirmed air support was backing government forces.

Thousands of Afghans have fled their homes and taken refuge in Lashkar Gah in the face of the new fighting, officials and residents say.

Afghan government officials said dozens of Taliban fighters were killed in fighting on the outskirts of Lashkar Gah as they attempted to overrun checkpoints. The Taliban, meanwhile, said scores of Afghan security personnel had died.

Fighting was also reported in other provinces.