Unusually heavy snowfall caused major disruption on South Africa's roads Saturday with people still stranded at midday after spending the night stuck in their vehicles.

The key N3 highway linking Johannesburg and the east coast city of Durban was one of the worst affected and several portions were closed, with even detours impassible, officials said.

Emergency services were working to reach people in their vehicles but it was still not clear how many were affected and in what condition they were, N3 Toll Concession operations manager Thania Dhoogra told the ENCA broadcaster.

"Emergency services have been working flat out through the night. They have been attempting to reach as many roads users as they can," Dhoogra said.

Blankets and meals had been delivered to some stranded motorists, the government of the KwaZulu-Natal province said in a statement at midday.

Trucks had been parked on the side of the road since Friday, Road Traffic Management Corporation communications officer Simon Zwane told AFP. "Buses travelling between provinces have been stuck at petrol stations for around seven hours," he said.

Motorist Muhammad Goolam told the Newzroom Afrika channel that he had spent the night in his car with his children outside the town of Harrismith, around 270 kilometres (170 miles) southeast of Johannesburg.

"Over 13 hours, food supplies out, I don't see us managing to drive out of here without any assistant from emergency personnel," he said.

Some areas had seen up to two metres (six feet) of snowfall, the Arrive Alive road safety campaign said in a post on X.

At least two people died from hypothermia after they were trapped in the heavy snow on the N3 in KwaZulu-Natal over the weekend.

During a briefing on Sunday afternoon, KZN acting Premier Thembeni Madlopha-Mthethwa said while some motorists still remain trapped, many have been rescued.

This comes after road users spent two nights in their cars as they were unable to move due to the heavy snow.