At least three people have been killed and several others injured in a blast in a chemicals shop in Pakistan's northwestern city of Peshawar.

The explosion on Saturday left several people trapped in a blazing building nearby.

"It was a low intensity explosion caused by a chemical reaction," Shafqat Malik, the local bomb disposal chief, told the news agency AFP.

The region's information minister had earlier said the blast was caused by a car bomb detonated by "remote control", but police confirmed to Al Jazeera that the blast was an accident.

Firefighters struggled to put out the flames in the nearby building where people were seen clinging to windows, shouting for help.

Several vehicles were damaged and the windows of adjacent stores were shattered in the blast. 

'Many injured'

Al Jazeera's Imran Khan, reporting from the capital, Islamabad, said: "It [the explosion] was in the middle of Peshawar, in a very busy district.

"There are many injured and an emergency has been declared at the Lady Reading hospital."

The explosion follows a string of attacks in the country.

On Friday, an attack on a mosque frequented by army personnel in the garrison city of Rawalpindi killed 37 people.