Scores of militants attacked a Pakistani security post near the Afghan border on Saturday, triggering a battle that left 18 combatants dead and cast doubt on claims by Pakistan's army to have regained control of a critical region.

A separate clash in the Swat Valley put more pressure on a disputed peace deal there, while a Taliban commander suspected in attacks on trucks carrying supplies to NATO and U.S. troops in Afghanistan surrendered to authorities, officials said.

The attack on the outpost occurred in the nearby Mohmand tribal region, where the army recently drove back militants threatening the strategically vital northwestern city of Peshawar.

About 100 insurgents attacked the Spinal Tangi post before dawn, the army said in a statement.

"Sixteen militants were killed in retaliatory fire. Two security forces personnel embraced shahadat (martyrdom)," it said.

Syed Ahmad Jan, a senior administrator in Mohmand, said three more troops were wounded.

Pakistani generals claimed earlier this year to have dismantled Taliban mini-states in Mohmand and the neighboring Bajur region, from where insurgents were attacking U.S. troops in Afghanistan as well as Pakistani forces and officials.

Yet militants still control much of the tribal belt along the mountainous frontier, where U.S. officials say Al Qaeda chief Usama bin Laden is probably still hiding, and have sought to expand toward previously peaceful areas.

Pakistani counterinsurgency efforts are currently focused on Buner, a hilly farming district near the Indus River that was infiltrated last month by Taliban militants.

The advance brought the Taliban to within 60 miles of Islamabad and triggered alarm in Pakistan and the West over the stability of the nuclear-armed country.

Pakistan's army says it has killed more than 100 militants and lost several soldiers since the fighting began on Tuesday. Militants have taken dozens more security personnel prisoner. Hundreds of civilians have fled the area.

On Saturday, the army said it was clearing bombs laid along one of two main roads it has secured and that it would soon let civilians travel to Buner's main town, Daggar. Warplanes have bombed militant strongholds further north.

Hundreds of Taliban gunmen seized Buner under cover of a controversial peace agreement in the neighboring Swat Valley. The government agreed to impose Islamic law in Swat and neighboring areas to halt two years of bloody and inconclusive fighting.

The United States, which is bankrolling Pakistan's government and army with billions of dollars and views eliminating militant enclaves in Pakistan as vital for success in Afghanistan, has likened the peace pact to a surrender.

Officials in Pakistan's northwest have sought to keep the peace pact alive, arguing that the Islamic law concession will persuade some to lay down their arms and isolate hard-liners.

But a cease-fire in the valley is under growing strain.

The army said troops exchanged fire with militants who refused to stop their jeep at a checkpoint in Swat on Friday and that five militants were detained while planting a bomb.

In better news for the government, a Taliban commander in the Khyber region, just west of Peshawar, surrendered Saturday after authorities put pressure on his tribe, local official Bakhtiar Khan said.

He said Iftikhar Khan Afridi was aligned with Baitullah Mehsud, the top Pakistani Taliban commander whom U.S. officials accuse of assisting insurgents in Afghanistan.

"We think his arrest will help reduce the attacks on the NATO supplies," the official said.

Militants have mounted repeated attacks on trucks that pass through the famed Khyber Pass in northwestern Pakistan on their way to Afghanistan to supply international forces there.