At least 13 people, including women and children, were killed after a gas cylinder blast caused a residential building to collapse in the southern port city of Karachi on Thursday, police said.

The cylinder exploded on the first floor of the multi-storey compound in Soldier Bazaar, a residential neighbourhood in the eastern part of the densely populated city, police said.

Seven children, including a two-year-old, were among the dead, said police official Summaiya Syed.

The police said they were investigating what triggered the explosion.

Emergency workers, who rescued over a dozen injured from the building, said there could be more people buried in the rubble.

A massive fire at a Karachi mall killed over 70 people last month.