Three children were rescued after spending hours in trees to escape rising waters near the Eastern Cape city of Mthatha, one of the areas hardest hit by the storm that struck on Monday, the provincial government said in a statement.

Six bodies were found in the city, which is about 800 kilometres (500 miles) south of Johannesburg, and a seventh body was found near a river in the rural Tsolo area, the statement read.

"The search is still ongoing regarding a minibus carrying school children that swept away earlier this morning," the provincial government said, without giving details on how many were onboard.

The province said it had deployed disaster management teams to assist people affected by the severe cold front, which also brought snowfalls to several areas.

Local media reports said residents of Mthatha had been trapped on rooftops in bitterly cold conditions early Tuesday.

Around 200 people had taken shelter in a community hall in the town of Butterworth, about 110 kilometres away, after their homes in an informal settlement were flooded, reports said.