A bomb blew a bus carrying Pakistani police and government workers off a high bridge Thursday, killing eight, as fighting between security forces and extremists flared across the country's northwest.

More than 200 people have been killed in a cycle of suicide bombings and clashes since longtime U.S. ally Pervez Musharraf quit as president and triggered a power struggle that caused the country's ruling coalition to collapse.

The turmoil has left the party long led by slain former leader Benazir Bhutto in a position to dominate the government and it has been toughening its stance against Islamist extremists.

However, its erstwhile coalition partner on Thursday echoed widespread opposition to Pakistan's role in the U.S.-led war on terror amid a surge in Taliban attacks.

Thursday's powerful blast incinerated the parked car in which the bomb was hidden and left a massive crater in the middle of the long, concrete bridge near the city of Bannu.

The badly damaged bus smashed through a railing on the side of the bridge and tumbled about 30 feet into a mostly dry river bed below.

Jalil Khan, the local police chief, said the bus was en route to a local prison to pick up several inmates. He said seven policemen and an education department official who had hitched a ride were killed.

Another 12 people — four police and eight civilians — were injured, he said.

There was no immediate claim of responsibility, though police said militants were the likely culprits.

Pakistan's 5-month-old civilian government initially sought to calm militant violence by holding peace talks.

But the initiatives have borne little fruit, and U.S. officials have been pressing for tougher action against insurgent strongholds in Pakistan's wild border region.

Musharraf resigned on Aug. 18, nine years after seizing power in a military coup, to avoid impeachment by political rivals who triumphed in February elections.

Former Prime Minister Nawaz Sharif pulled out of the coalition a week later over its failure to restore judges purged by Musharraf last year.

Lawyers who agitated for more than a year in favor of the judges and against Musharraf, restarted their rallies Thursday.

Several thousand blocked roads in a string of major cities. They also chanted slogans against Asif Ali Zardari, Bhutto's widower and the favorite to replace Musharraf when lawmakers select a new president on Sept. 6.

Sharif's supporters largely stayed away from the protests, which were smaller than in the past.

However, a leader of his party on Thursday called for a halt to a weeks-old military offensive in the Bajur region, saying the estimated 200,000 people who have fled the fighting to makeshift camps were suffering too much.

"This war should be stopped. Talking through the language of the bullet should be stopped. On one side, a political solution to this problem should be sought, and on the other side, the refugees should be given better treatment," Chaudhry Nisar Ali Khan told reporters after a meeting with the prime minister.

Pakistan's army, which U.S. officials complain has been ineffective in preventing militants from mounting cross-border attacks into Afghanistan, is now fighting insurgents in at least three areas of the northwest.

Army spokesman Maj. Murad Khan said two paramilitary troops died and five were wounded when militants attacked their convoy in South Waziristan on Wednesday.

He said the troops shot dead a suicide bomber riding a motorcycle before he could approach them. Several militants were detained, Khan said.

Troops are also battling militants in Bajur, another tribal area some 200 miles to the north.

According to an official and a witness, volunteers guarding a tribal council in the Salarzai area of Bajur on Thursday shot and killed another suicide bomber before he could strike.

The dead man was carrying an explosives-filled vest, said Fazl Rabi, a local police commander. Two accomplices were captured, he said.

Pakistan's military insists it is doing what it can to contain militants and prevent them from moving against NATO and Afghan troops on the other side of the border.

Pakistani army chief Gen. Ashfaq Parvez Kayani met Adm. Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, and other top American commanders on an American aircraft carrier in the Indian Ocean on Tuesday to discuss security strategy, officials said.

"This was a prescheduled meeting aimed at discussing security matters at strategic level. The discussion was held in an open and cordial manner," a Pakistani military statement said.

Army spokesman Maj. Gen. Athar Abbas said the commanders analyzed the security situation in the region and that no new agreements were struck.