Hundreds of pro-Taliban militants stormed and overran a key Pakistani paramilitary fort in the restive tribal region bordering Afghanistan, killing at least seven soldiers while losing up to 50 of their own men, the army said on Wednesday.

Another 20 personnel of the paramilitary Frontier Corps were missing, following the attack on the Sararogha fort in South Waziristan tribal agency, by militants armed with rockets and automatic weapons. The insurgents blew up a wall of the fort before entering the structure, the army said.

Over 400 militants attacked the Sararogha fort at midnight and later captured it, military spokesman Major General Athar Abbas told reporters. He said 40 to 50 militants and seven Frontier Corps personnel were killed in the fighting.

The fort, located about 80 kms from South Waziristan's main town of Wana, was manned by 42 personnel. While 15 personnel managed to reach another Frontier Corps fort in Jandola, 20 others were missing.

The army said in a statement that the exact location of these 20 personnel is not known.

There was a heavy exchange of fire throughout the night and the militants were targeted with artillery from two locations, the statement said. The militants then blew up a wall of the fort, using explosives late at night, and entered the structure.

Local officials were quoted as saying that the Taliban had captured some of the security personnel in the fort but this was not confirmed by the army. Earlier reports had said that up to 30 paramilitary troops were feared killed in the attack.

Local authorities have convened a jirga or council of tribal elders to trace the missing soldiers.

The area is a stronghold of the Mehsud tribe and Tehrik-e-Taliban Pakistan commander Baitullah Mehsud, blamed by President Pervez Musharraf [Images] for masterminding a string of suicide attacks, including the assassination of former premier Benazir Bhutto [Images].

Musharraf has also accused Baitullah Mehsud of recruiting and training suicide bombers in South Waziristan, a lawless region bordering Afghanistan. Mehsud has denied involvement in Bhutto's killing.

Last week, security forces had repulsed an attack by over 300 militants on Ladha fort, in South Waziristan. Over 50 rebels were also killed in that attack, the Army said