Five children have died in a fire in an informal settlement in South Africa's capital Pretoria, local media report.

According to local reports the mothers of the children - three boys and two girls aged between one and seven - had been left alone at home overnight.

The children's bodies were discovered by firefighters who put out the blaze, and the mothers have been arrested and taken to the local police station for questioning.

The cause of the fire is not yet known and investigations are ongoing.

"We call upon parents and caregivers to ensure that children are always left under the care of an adult and in a safe environment," the City of Tshwane's emergency services department spokesperson Charles Mabaso is quoted as saying.