Troops and helicopter gunships killed about 40 Taliban militants while four people, including a politician, were injured in a roadside bomb in northwest Pakistan, officials said Monday.

More than 24 extremists with links to Al-Qaeda were killed on Sunday near the Afghan border in the Bajaur tribal region, where Pakistani security forces launched a major offensive against Islamic militants in August.

"Helicopter gunships and artillery pounded hideouts of militants, killing at least 24 rebels and wounding 10 others," a security official told AFP.

Shelling began in the afternoon and continued into the early hours of Monday, he said, adding four militants and two locals were also killed in an exchange of fire between a tribal lashkar (force) and rebels in Bajaur.

The tribal force was formed last week to act against militants hiding in the area, who local tribesmen say are undermining their power structure.

The Pakistani military says more than 1,000 rebel fighters have been killed since it launched its offensive in Bajaur, including Al-Qaeda's operational commander in the region, Egyptian Abu Saeed Al-Masri.

On Monday ten Islamic extremists died in a gunbattle with soldiers in the Khawazakhela district of the Swat valley during an ongoing military operation against fighters loyal to local cleric Maulana Fazlullah.

"Ten militants were killed in an operation by our security forces," a military official told AFP, adding there were no casualties among troops.

Separately four people, including a local leader of the ruling Awami National Party (ANP), were injured when a roadside bomb struck their vehicle in the neighbouring tribal district of Dir, an administration official said.

"Sameen Khan and three others were injured when a remote control bomb planted on a roadside exploded," Abdul Rashid Khan told AFP.

Militants have recently targeted several ANP politicians and their relatives, and the party chief Asfandyar Khan Wali narrowly escaped a suicide attack at his home in the town of Charsadda earlier this month.

The mountainous Swat valley was until last year a popular tourist destination where many Pakistani city dwellers went for their annual holidays and it featured Pakistan's only ski resort.

But it has been turned into a battleground since Maulana Fazlullah launched a violent campaign to enforce harsh Islamic Sharia law in the region.

Many of Pakistan's tribal regions have been wracked by violence since thousands of Taliban and Al-Qaeda rebels fled to the country after the US-led invasion of Afghanistan in late 2001.