Fire-fighters work to extinguish fires after a bomb explosion in Peshawar, located in Pakistan's restive North West Frontier Province October 28, 2009. [Agencies]

PESHAWAR, Pakistan: A car bomb tore through a crowded market in northwestern Pakistan on Wednesday, killing 86 people hours after US Secretary of State Hillary Rodham Clinton arrived in the country to show American support for its campaign against Islamist militants.

More than 200 people were wounded in the blast in the main northwestern city of Peshawar, the deadliest in a surge of attacks this month. The government blamed militants seeking to avenge an army offensive against al-Qaida and Taliban close to the Afghan border.

TV footage showed wounded people sitting amid the debris as people grabbed at the wreckage, trying to pull out survivors before carrying them down narrow alleys to hospital. One two-story building collapsed as firefighters doused it with water.

Clinton, on her first visit to Pakistan as secretary of state, was three hours' drive away in the capital of Islamabad when the blast took place. Speaking to reporters on her plane, she praised the army's anti-Taliban offensive in South Waziristan and promised a new era in relations between Pakistan and the United States.

North West Frontier Province Information Minister Mian Iftikhar Hussain told reporters outside a city hospital that at least 80 people had been killed and 200 wounded in the blast. Many of the victims were women and children.

No group claimed responsibility for the bombing, but that is not unusual, especially when the victims are Pakistani civilians.

Three bombs have exploded in Peshawar this month, including one that killed more than 50 people, part of a barrage of at least 10 major attacks across the country that have killed some 250 people. Most have targeted security forces, but some bombs have gone off in public places, apparently to sow fear and expose the weakness of the government.

The Taliban have warned Pakistan that they would stage more attacks if the army does not end a new ground offensive in South Waziristan tribal region, where the military has dispatched some 30,000 troops to flush out insurgents. South Waziristan is a major base for the Pakistani Taliban and other foreign militants.

Hussain blamed the militants for Wednesday's attack.