A homicide bomber riding a rickshaw attacked a police checkpoint and gunmen fired on officers guarding a bank in Pakistan's northwest Tuesday, killing five people and testing the new government's fledgling peace process.

Police said the homicide attacker rode up to the checkpoint on a bridge in the garrison town of Bannu. He detonated his explosives when officers signaled him to stop, said Dar Ali, the Bannu district police chief.

The army said two civilians and one policeman were killed. Police said four of their officers were wounded.

There was no claim of responsibility, and it was not clear whether police had prevented an attack on a different target.

Aurangzeb Khan, another police official in Bannu, said the checkpoint was near the office of a "sensitive institution" — an apparent reference to an intelligence agency.

Bannu is also a hub for the tens of thousands of Pakistani troops deployed in the border region as part of the U.S.-led war against terrorism.

Those troops, as well as Taliban and Al Qaeda militants, have been observing an almost complete cease-fire since a new Pakistani government took office five weeks ago.

The coalition government, made up of opponents of U.S.-backed President Pervez Musharraf, is pursuing negotiations through tribal elders designed to curb rising Islamic militancy.

The most publicized negotiations are in South Waziristan, a tribally governed region on the Afghan border. Those talks appear to have snagged over demands for an army withdrawal.

Farhatullah Babar, spokesman for the party that leads the coalition government, said there was "deadlock in the sense that the militants have said they demand that the troops be withdrawn, but they have not said the talks have broken down."

Spokesmen for Taliban militants in Pakistan could not be reached for comment Tuesday.

The gunmen struck in Matta, a former militant stronghold in the scenic Swat Valley, where troops were deployed to repel the spread of Islamic militancy from the border region last year.

Humayun Khan, a police official in Matta, said several gunmen approached a bank in the town on foot early Tuesday and shot to death two officers standing guard.

Khan blamed "local Taliban" for the attack, an apparent reference to supporters of Maulana Fazlullah, the fundamentalist cleric who temporarily seized control of parts of the valley last year.

The government last month released Fazlullah's father-in-law from six years in detention. The ailing leader, Sufi Muhammad, agreed to continue his campaign for the imposition of Islamic law in the region by purely peaceful means.

The deal was a first success for the government's efforts to persuade militants to lay down their arms and distance itself from Musharraf's more forceful tactics, which many here argue only fueled a wave of Islamist violence in Pakistan over the past year.

However, son-in-law Maulana Fazlullah has vowed to continue his armed struggle.

Washington, which strongly backed Musharraf, is voicing cautious support for the new emphasis on negotiations. It is co-funding a plan to flood Pakistan's wild tribal belt with development aid as well as to beef up locally recruited security forces.

But U.S. officials also want Pakistani security forces to keep up the pressure on militants along the border, arguing that earlier deals struck under Musharraf allowed Islamic militants to regroup and plan more attacks in Afghanistan, Pakistan and the West.

"We will not be satisfied until all the violent extremism emanating from the (tribal belt) is brought under control," U.S. Deputy Secretary of State John Negroponte said Monday.