People gather on rooftops to survey a damaged street following a car bombing in Charsadda, Pakistan on Tuesday. (Mohammad Sajjad/Associated Press)

Early reports say at least 24 people died in an explosion in the city of Charsadda in northwest Pakistan on Tuesday.

At least 102 people were wounded in the blast.

Police said the explosion occurred at a crowded market in the city, which is about 40 kilometres north of Peshawar, the capital of Pakistan's North West Frontier province.

Liaqat Ali Khan, the senior police chief in Peshawar, said the blast was caused by about 40 kilograms of explosives stuffed into a van.

The blast destroyed cars and badly damaged several stalls and shops. The dead and injured were ferried to hospital along roads littered with debris.

Another police official, Riaz Khan, said: "I had just passed through this place hardly two minutes before the blast. I felt it myself. We got back and saw destruction everywhere."

The Peshawar area has now been hit by three attacks in as many days. On Monday, a suicide bomber detonated his explosives near a group of police officers in Peshawar, killing three other people and injuring five.

A blast in a market less than two weeks ago killed 112 people, making it the deadliest attack in the country in more than two years.

The wave of explosions comes as the Pakistani army continues its offensive against militants in the region of South Waziristan, where the Taliban and al-Qaeda have their sanctuary along the Afghan border.

The army has claimed to have killed nine militants in the latest fighting, although that figure cannot be corroborated as the combat zone is closed to the media.

With files from The Associated Press