Pakistani troops hunting for terrorists Saturday in a remote tribal region along the border with Afghanistan killed 11 people who were riding in a minibus that did not stop at a rural checkpoint, an army spokesman said.

Pakistani and U.S. officials, meanwhile, vigorously denied an Iranian radio report that Al Qaeda leader Usama bin Laden (search) had been caught "a long time ago." Bin Laden is thought to be hiding in the region now being intensively searched by Pakistani forces.

The Pashtun service of Iran radio said the Bush Administration was waiting until closer to the presidential election to produce bin Laden.

In the killings Saturday, Gen. Shaukat Sultan (search) said troops opened fire on the minibus after someone fired on the paramilitary forces at a roadblock in Zeri Noor, a village just outside of Wana, the main town in tribal South Waziristan. Counterterrorism operations there earlier this week netted 25 suspects.

Sixteen people were arrested.

The deaths were sure to raise the anger of fiercely independent tribal leaders already enraged by the presence of troops in their territory.

Residents said they were outraged by the shootings, and disputed government claims that someone in the bus fired first.

"Innocent people were killed in this operation. It was a civilian vehicle and the army is at fault," said Zia Uddin, a 36-year-old school teacher.

Troops increased their presence Friday in Wana, 190 miles west of the capital, Islamabad, in part to provide additional security to against religious violence during the Shiite Muslim Muharram holiday.

On Saturday, a suicide bomber blew himself up near a Shiite mosque in Rawalpindi, a city adjacent to the Pakistani capital. The bomb exploded prematurely, killing the attacker and injuring two people, Sultan said.

Muharram, which starts in March, marks a month when Shiites mourn the seventh-century death of Hussein, grandson of Islam's prophet, Muhammad.

Pakistani authorities stepped up security at airports nationwide to the highest level Saturday in anticipation of the holiday. They said the move was not linked to the counterterror activities along the border, and that there was no specific threat.

In the minibus shooting, witness Allah Dad told AP the vehicle was filled mostly with Afghan refugees on their way to the border. A taxi driving near the minibus also was hit, and the driver killed, Dad said.

"There is a lot of tension in the area and a lot of troops," Dad said. "The roads to Afghanistan have been sealed."

In a separate incident Friday, armed men tried to sneak into a military compound in Wana, sparking a shootout, Sultan said. One soldier was injured by a rocket fired by the attackers, local official Mohammed Azam Khan said.

Despite deep local opposition, Pakistani forces have been slowly increasing their presence in the tribal areas under pressure from Washington to crack down on Al Qaeda (search) and Taliban (search) suspects, who are believed sheltering in the region.

Authorities have deployed rapid reaction forces to specific areas along the border with Afghanistan, a mountainous expanse that runs 2,000 miles from the Himalayas in Pakistan's northern territories to the desert of southwestern Baluchistan.

Meanwhile, U.S. Coordinator for Counterterrorism Cofer Black was in the capital Islamabad for talks with Pakistani officials. He met Friday with Tariq Osman Hyder, a senior Foreign Ministry official, to discuss cooperation in the global campaign against terrorism, a ministry statement said.

The U.S. Embassy confirmed Black's arrival but would give no details about his discussions.