About 90 rebels were killed by Pakistani security forces in two clashes on Friday in the troubled South Waziristan region bordering Afghanistan, which has witnessed an upsurge in activities by pro-Taliban militants.

The fighting erupted two days after hundreds of militants stormed a paramilitary outpost at Sararogha in South Waziristan, killing at least seven troops. Fifteen more personnel were reported missing following the attack.

Military spokesman Maj Gen Athar Abbas said about 90 militants were killed in the two separate skirmishes today and four security forces personnel were injured. The clashes erupted after the militants attacked the security forces, he said.

"Today at 12:30 pm, a convoy of security forces moving on Jandola-Wana Road was fired upon with small arms and rockets. The security forces retaliated and engaged the militants with small arms and rockets," he said.

The gun battle continued for an hour. Though the exact number of casualties among the militants was not known, "it is estimated that 20-30" rebels were killed, Abbas said. Four security forces personnel were injured and two vehicles were damaged in the clash, he said.

The second clash occurred at Ladha Fort, an outpost manned by Frontier Corps personnel. Militants engaged the fort with small arms and rockets at 10 am. "A large number of militants started gathering around the fort at 3 pm. The security forces used artillery, mortars and small arms to engage them," Abbas said.

About 50 to 60 militants were killed and many more were injured before the rebels dispersed. The security forces suffered no casualties, he said.

The militants took away the bodies of their dead, Abbas said.

An earlier statement from the army said gunship helicopters had targeted two vehicles in the vicinity of Siplatoi Fort in South Waziristan on Thursday and killed eight militants.

The army also denied claims by local Taliban commanders that they had captured Siplatoi fort after Frontier Corps personnel manning it surrendered. The army said the troops are still manning the fort.

Meanwhile, security forces conducted a search operation in Tank district on the outskirts of South Waziristan, district police chief Mumtaz Zareen said. Four persons were arrested during the operation.

Zareen said over 60 people were arrested a week ago in a similar operation but 30 were freed later while the others are still being questioned.

The area where the Ladha fort is located is a stronghold of the Mehsud tribe and Tehrik-e-Taliban Pakistan commander Baitullah Mehsud. President Pervez Musharraf [Images] has blamed Mehsud for masterminding a string of suicide attacks, including the assassination of former premier Benazir Bhutto [Images], and recruiting and training suicide bombers in South Waziristan.

Mehsud has denied involvement in Bhutto's killing.