Police in South Africa have launched a manhunt after 12 people were killed in a mass shooting at an informal settlement in Johannesburg.

At least 10 suspects, heavily armed with rifles, entered the Jumpers Informal Settlement in the suburb of Cleveland late on Tuesday night and opened fire before fleeing in a white vehicle, police said.

The motive for what police called a "heartless" and "barbaric" attack, in which another nine people were injured, is still being investigated.

Members of the Jumper's community believe the shooting may be linked to a turf war between groups of illegal miners living in the area.

Illegal mining has been on the increase in South Africa, which has one of the highest murder rates in the world.

Shootings in informal settlements are not uncommon, sometimes linked to gang violence and personal disputes.

The local police department said its officers responded to a "complaint of shooting in progress" at about 23:10 local time (21:10 GMT) on Tuesday.

"It is alleged that more than 10 suspects were dropped off by a white Toyota Quantum near a petrol station in Cleveland," the police said in a statement.

"The suspects allegedly entered the informal settlement through both entrances and moved through the area, opening fire on residents and community members at multiple locations before fleeing the scene in the same vehicle," the statement added.

Police said eight men and three women died at the scene, while another man died from his injuries in hospital.

At least nine others were taken to various medical facilities for treatment of gunshot wounds.

The police have said that the motive for the attack is not known and forms part of the investigation.

During a visit to the scene on Wednesday, provincial police commissioner Lt Gen Tommy Mthombeni reiterated this stance, but added that investigators could not rule out a connection to illegal mining.

"As you know, this area is adjacent to the illegal mining area. We are having those suspicions," he told reporters, calling the attack "heartless" and "barbaric".

Illegal mining is a lucrative, informal activity - with groups targeting disused gold mines and selling their finds on the black market.

The trade is often violent - earlier this year, South African President Cyril Ramaphosa deployed the military to some communities to help close down operations.

Last year, nine people were killed in a mass shooting at a tavern in Johannesburg.

There are about three million legally held firearms in South Africa and at least the same number of unlicensed weapons, according to statistics cited by Gideon Joubert from the South African Gunowners' Association.