At least 16 people, including children, have died after a gas leak at a South African slum near Johannesburg, emergency services said, according to AFP.

The Wednesday night disaster, thought to be linked to illegal mining activities, occurred at the Angelo informal settlement near the district of Boksburg, east of Johannesburg, the report said.

"We have got 16 on scene now that are confirmed dead, and the intervention of paramedics managed to revive some others and they were taken to hospital," emergency services spokesman William Ntladi said.

Of those in hospital, four are in "critical" condition while 11 are in "serious but stable" condition, he said. One, who he described as a minor, was fully conscious, he added.

Five women and three children were among the dead.

Emergency services received a call around 8:00 p.m. local time about a gas explosion, but on arrival they discovered it was "a gas leakage from a cylinder" containing a "poisonous gas", Ntladi said.

Preliminary information suggests the gas was being used "as part of illegal mining activities," he added.

South Africa is home to thousands of illegal miners nicknamed "zama zamas" which means "those who try their luck" in Zulu.

Thousands of the unregistered miners scavenge obsolete mines for gold under arduous and often perilous conditions.

Boksburg, a middle-class suburb of Johannesburg, was previously the scene of a massive gas tanker explosion that killed 41 people on Christmas Eve last year, when a truck carrying liquefied petroleum gas (LPG) got stuck under a bridge, triggering a leak and blast.