Islamabad  - At least 20 militants and four troops were killed on Wednesday in an operation by the Pakistan Army against Taliban fighters in the restive tribal areas bordering Afghanistan, an army spokesman said.

The clashes took place as thousands of troops, backed by helicopter gunships, launched a major offensive to take control of the Taliban's command and control system in the Rashkai area of Bajaur tribal district.

"We cleared the area of the insurgents and have complete control over it," army spokesman Major Murad Khan told Deutsche Presse-Agentur dpa.

A large quantity of ammunition and improvised explosive devices were discovered at the militants' headquarters, he added.

"According to initial reports at least 20 miscreants were killed and numerous injured while four soldiers were also martyred."

Pakistani troops have been fighting the Taliban since August 6 in Bajaur district, from where the rebels target US-led international forces in neighbouring Afghanistan.

According to official figures, around 600 militants have been killed in the action. But the operation was halted on September 1 after lawmakers from the tribal belt threatened to withdraw their support for Asif Ali Zardari in the presidential elections.

However, it was resumed on September 6, the same day Zardari won the presidential vote.

The operation has triggered a mass exodus from Bajaur to safer areas in the adjoining North-West Frontier Province.

Pakistan is under growing pressure to crack down on militants entrenched in its tribal areas.

Concerned over the country's inability to eliminate the militants' hideouts, United States forces deployed in Afghanistan have carried out several missile attacks and at least one ground attack in Pakistan's tribal areas. (dpa)