At least seven people have died in a large bomb explosion in Karachi in southern Pakistan.

The device appears to have been placed by a stall at a market place in the centre of the city.

Witnesses said there was a huge explosion, with windows in nearby buildings blown out and a large crater left in the road.

Nobody has claimed responsibility for planting the device, but the governor of the province of Sindh -- of which Karachi is the capital -- has accused Indian intelligence services of carrying out the attack.

India has strongly denied the allegation.

Singh province was placed under direct rule last year in an effort to curb violence which has resulted in hundreds of deaths in Karachi.

From the newsroom of the BBC World Service