At least 40 militants and eight security personnel have died in fierce fighting in Pakistan's troubled South Waziristan region after troops launched an operation in the tribal area along the Afghan border.

Thirty-two security personnel were injured in the clashes that erupted after hundreds of troops were sent to South Waziristan on Wednesday following a sharp increase in attacks on security forces by pro-Taliban militants.

The army said it had also captured 30 militants while many rebels were injured in the fighting, in which the troops were backed by helicopters and artillery.

The security forces conducted operations at Spinkai Raghazai, Nawazkot and Tiarza in South Waziristan and cleared these areas of militant strongholds and hideouts, a statement from the army said.

The security forces moved three tanks to the Jandola area to protect the movement of military convoys, the army said.

The militants had attacked a security forces convoy near Jandola on Wednesday.

Officials in South Waziristan have said that about 600 soldiers backed by heavy artillery and tanks were conducting operations against the Taliban, who were using rockets and automatic weapons to hit the positions of security forces.

On Wednesday, a soldier was killed and two more were injured when militants fired rockets at a security forces camp at Razmak in North Waziristan while two security forces personnel were injured in an improvised explosive device blast at Ghatghundai in South Waziristan.

The army had said on Wednesday that a decision was made to reinforce security forces' check posts and camps in South Waziristan due to the recent attacks by militants.

South Waziristan, a stronghold of Tehrik-e-Taliban Pakistan commander Baitullah Mehsud, has witnessed fierce clashes over the past two weeks. Hundreds of militants have made at least three attempts to storm the Ladha fort, a British-era base, since January 12, during which nearly 140 troops were killed.

Though there is a temporary truce between security forces and rebels in North Waziristan, Mehsud's men have entered the region from South Waziristan and attacked troops.

President Pervez Musharraf [Images] has accused Mehsud of masterminding the assassination of former premier Benazir Bhutto [Images] and carrying out a series of suicide attacks across Pakistan.