ISLAMABAD, Pakistan — Security forces clashed with militants across Pakistan's wild tribal belt Wednesday, trading fire with insurgents in a health center and repelling a major assault on an outpost in a region known as an al-Qaida safe haven.

As many as 49 insurgents died, officials claimed.

Troops are engaged in bloody offensives against violent Islamic extremists in the northern Swat valley and in Bajur, a region considered a launchpad for Taliban operations into neighboring Afghanistan and a possible hideaway for Osama bin Laden.

In a sign that a third front may be opening up, the military said dozens of insurgents assailed a fort in the South Waziristan region.

Troops guarding Tiarza Fort and a checkpoint on a nearby bridge "repulsed the attack," killing 11 militants, a military statement said.

In the deadliest fighting, troops rained gunfire and artillery on militants holed up in a health center in Bajur, killing 30, said military spokesman Maj. Murad Khan.

The military assessed the toll with the help of intercepted radio traffic among the insurgents, he said, claiming that no troops were hurt in the hours-long battle.

In what appeared to be separate attacks, police said eight militants died when government forces fired on suspect vehicles in two areas of Bajur on Wednesday morning.

The reported casualties could not be verified independently. Few reporters work in the tribal region for fear they could become a target in the conflict. Spokesmen for the militants could not be reached for comment.

Officials say hundreds of militants have died in the weeks-old operation, while residents say civilians have also been killed.

An estimated 200,000 people have fled to safer areas.

Suspected militant hideouts in South Waziristan have been targeted in a stream of suspected U.S. missile attacks, including one that killed a senior al-Qaida commander in July.

Aminullah Wazir, a shopkeeper in Wana, the region's main town, said security forces imposed a curfew in the area Wednesday. Shops were shut and the streets deserted, he said.

"We heard shelling and gunfire almost all night," Wazir told The Associated Press by telephone.

Pakistan's five-month-old government initially dabbled in peace talks with militants. But the initiatives have borne little fruit, and U.S. officials have been pressing for stiffer action against insurgents they blame for soaring violence in Afghanistan.

Pakistan this week banned the Pakistani wing of the Taliban movement after it claimed responsibility for a double suicide bombing that killed 67 people at an arms factory near the capital.

On Tuesday, gunmen fired at the car of a senior U.S. diplomat in the northwestern city of Peshawar and a bomb killed seven at a roadside restaurant near the capital, Islamabad.

Tensions have also flared in the southern metropolis of Karachi, Pakistan's economic and financial hub.

A dispute on Tuesday between student followers of two feuding political parties — one secular, one Islamist — escalated into a gunbattle that left three people dead on Karachi's university campus, officials said.

Musharraf resigned Aug. 18 to avoid impeachment charges, triggering a scramble for power that has brought down the coalition of political parties that ended the former coup leader's nine-year rule.

Lawmakers are expected to elect Asif Ali Zardari, the widower of slain former leader Benazir Bhutto, as Musharraf's replacement on Sept. 6.

Pakistani officials played down a Financial Times report this week claiming Zardari had severe mental health problems as recently as 2007, though they acknowledged he had suffered from stress related to alleged torture in prison and separation from his family.

Zardari spent years in prison on corruption allegations.

"He only received counseling," said Wajid Hasan, Pakistan's ambassador in Britain and a friend of Zardari's.

"I have spent long periods of time with him in the past two years," Hasan said Tuesday, adding that recent examinations "showed that he is fit."

Zardari's party, which is courting smaller parties to shore up its parliamentary majority, has begun toughening the government's line against militants.

Still, Pakistanis and the country's Western backers worry that the political turmoil is hindering efforts to counter rising Islamic extremism and shore up the flagging economy.

On Wednesday, the Karachi stock exchange's benchmark 100-share index fell another 3 percent. The index has plummeted by more than 40 percent since April and stands at its lowest level in more than two years.