Some 30 people are reported to have been wounded in the explosion.

Police say the blast was caused by a bomb which rocked an illegal gambling den run by a local crime gang.

One report said the den was known as the Rummy Club, and is located in a poorer part of the south of the city, where gambling is an illegal but popular activity.

The city, Pakistan's commercial capital, has seen a series of political and ethnic attacks which claimed 775 lives last year.