ISLAMABAD (BBC) -- A bomb blast has killed at least six people in Pakistan's northwestern city of Peshawar, police say.

At least 21 people were injured in the explosion in a busy shopping district of the city. Many of the wounded were taken to hospital.

The bomb was reportedly planted in a cart and went off as people were preparing for the Eid festival to mark the end of the holy month of Ramadan.

No-one has so far claimed responsibility for the blast.

Crowded area

The explosion occurred at 1710 local time (1210 GMT).

"The bomb was fitted in a cart parked in a crowded area, where people were busy shopping for Eid," Riffat Pasha, local police chief told Reuters news agency.

The BBC's Barbara Plett at the site of the blast says she saw the wreckage of the cart and blood stains.

Some witnesses were quoted as saying people were lying "in pools of blood".

The blast was the most series in a number of explosions in Peshawar over the last month, BBC correspondent says.

Police have so far given no explanation who was behind the attacks.

The latest blast happened near the headquarters of Pakistan's border security forces, she says.

Police cordoned off the area immediately after the explosion.