The explosion went off in a bank building in the Sher Shah area and social media and TV footage showed the two-floor structure’s windows and doors blown out, with documents scattered across a wide area.

Cars and motorcycles parked nearby were also damaged.

Provincial police told AFP a bomb disposal squad was investigating, but “apparently the leakage of gas was the cause”.

They said 12 people had been confirmed killed, and 13 were being treated for injuries.

Explosions caused by faulty gas cylinders — which are used for cooking as well as in cars –- are common in Pakistan.

Karachi, which is responsible for 60 percent of Pakistan’s economic output, has long endured creaky infrastructure, illegal construction and failing municipal services.

AFP