PESHAWAR, Pakistan (AFP) - Pakistan's military said Monday six militants were killed when their bomb exploded as troops pushed on with an offensive to regain control of northwest Swat valley's Taliban-held capital.

A military official who did not want to be named said that the six men died overnight in Kabal town about 20 kilometres (12 miles) west of Swat's urban hub Mingora, where troops are fighting fierce street battles with insurgents.

"They were trying to plant a bomb outside a mosque but it exploded on them," the official told AFP. "The dead bodies of six armed militants are still lying near the mosque."

He said Pakistan's security forces were still battling on the streets of Mingora, the business and administrative hub of the scenic region which has been ripped apart by a two-year insurgency by Islamist extremists.

"According to information I received, militants are retreating from different fronts but we are still receiving fire from some pockets of resistance," he said.

A security official, who also requested anonymity as he was not authorised to speak to the media, said that the military continued to advance inside Mingora, regaining control of several key areas.

"Militants are on the run, their dead bodies are laying in streets" he said.

Although the military has bases inside Mingora, the town has been under effective Taliban control for weeks.

Helicopter gunships, meanwhile, shelled militant hideouts in Peochar and Malam Jabba - mountainous areas northwest of Mingora which are Taliban bastions.

Reporters and humanitarian workers have mostly been barred from visiting the conflict zone and telephone land lines and mobile signals appear to have been cut in Mingora, making the military's claims impossible to verify.

Pakistan says more than 1,100 militants and 66 soldiers have died in the onslaught launched in the districts of Lower Dir on April 26, Buner on April 28 and Swat on May 8, but those tolls cannot be confirmed independently.

More than 1.7 million terrified civilians have already fled the military offensive, which Islamabad launched after Taliban militants advanced last month to within 100 kilometres (60 miles) of the capital Islamabad.