Pakistan troops have surrounded Ayman al-Zawahiri, Al-Qaeda leader Osama bin Laden's second-in-command, in South Waziristan, near the Afghan border, according to reports.

President Pervez Musharraf told CNN it might be a 'high-value target'. But "I can't say who", he added.

The development came as Pakistani troops launched a new ground and aerial offensive against Al-Qaeda and Taliban terrorists in the region, where 40 people, including 16 paramilitary personnel, were killed in fighting on March 16.

The troops used helicopter gunships in the operation, defence ministry spokesman Major General Shoukat Sultan said in Islamabad.

Prior to the operation, he said, the authorities asked locals to leave the area.

"Thursday's operation is continuation of the operation first launched on March 16th," he said.

"The militants and their supporters showed stiff resistance on first day of operation."

With Inputs from PTI