At least 12 people were killed Monday when Taliban militants and local tribesmen exchanged heavy gunfire in Pakistan's restive tribal district of Bajaur, security officials said.

The fighting started when an army of volunteers from the Salarzai tribe tried to set ablaze the houses of the insurgents, who have been fighting government forces since early August when government troops launched an operation in the region to retake a strategically important checkpoint from the rebels along the Afghan border.

"At least nine locals and three Taliban - including their commander in the area, Abdul Mutallab - died in the firefight while six more people were injured," a security official said on the condition of anonymity.

In some areas of Bajaur, locals have been defying the Taliban and its hard-line shariah law. Members of three tribes - the Salarzai, Tarkhani and Utmankhel - have announced they intend to defend their respective areas against the fundamentalist Islamic group that ruled Afghanistan until it was ousted in late 2001 in a US-led invasion.

Bajaur is a sanctuary of al-Qaeda and Taliban militants launching crossborder attacks on international forces in Afghanistan.

Some military experts said a success by Pakistani forces against Taliban and al-Qaeda fighters in Bajaur would be a major breakthrough in the fight against rising Islamic militancy in the country.

So far, more than 500 militants and dozens of soldiers have died in the operation.