Karachi: At least 15 people were killed and 40 others were injured when a powerful bomb went off at a gambling den in the southern Pakistani city of Karachi on Thursday.

The explosion occurred within the compound of a building in Ghasmandi area in the old quarters of Karachi.

A gambling den is located on the ground floor of the building, local residents said. A news channel reported that the blast was part of a fight between two gangs to control the gambling den.

Officials at the Civil Hospital said that they had received 15 bodies. Nearly 40 injured were taken to several hospitals. Ten of the injured were in a serious condition, officials said.

A large crowd gathered at the site of the blast as residents helped transport the injured to hospital. Security forces cordoned off the area shortly after the blast,which was heard from several kilometres away.

Bloodstains and discarded footwears lay scattered at the site of the blast. The explosion caused a crater and many of the injured were hit by splinters. Hundreds of people were present in the gambling den at the time of the blast.

However, no group has claimed responsibility for the attack so far. Officials of the bomb disposal squad dismissed an earlier report that the blast was caused by a grenade. They said evidence indicated that a planted bomb was used in the attack.