Media playback is unsupported on your device Media caption At least 13 people were killed in the landslide

A rare rockslide in Pakistan's city of Karachi has hit several makeshift homes, killing 13 people including seven children, officials say.

The landslide struck early on Tuesday, burying homes in Gulistan Johar district under a mass of rock and mud.

Rescue workers are using mechanical tools to clear the rubble.

Police and officials are investigating the cause of the landslip, including the possibility of sabotage by land grabbers, reports say.

Landslides are rare in Karachi, where most of the land is mud and sand - but the huts appeared to be part of a slum situated on land that had been flattened by cutting off the side of a ridge, the BBC's Ilyas Khan in Islamabad reports.

Image copyright EPA Image caption The rockslide crushed homes on a plot of land carved out of a hill

Image copyright AFP Image caption Members of at least two families were killed

"It fell when they were asleep. There were big rocks," Rizwana, a local woman who lost five relatives in the rockslide, told Reuters.

"My poor father alone tried to move the rocks but he couldn't do so. It was very dark here at that time and visibility was very low," she said.