SIMIC

Seizing keys to the blocked trucks, militants, 15 of whom have been arrested, demonstrated against pump prices as they rose to record highs, reported Bloomberg.

The road between Mbombela, 350 kilometres (217 miles) east of Johannesburg, and White River has been obstructed by parked trucks, as has N4 highway connecting to Maputo.

Callum MacPherson, regional operations manager at Hi-Tech Security Nelspruit said a group of minibus-taxi operators started blocking trucks and taking drivers' keys at around 1am local time, according to freight drivers Bloomberg spoke to.

The blockades continued into the afternoon, said Solange Soares Nicholson, spokeswoman at Trans African Concessions (Pty) Ltd., which operates the N4 highway.

Other blockages were caused by a truck spilling coal across the road outside the town of Emalahleni, west of Mbombela, she said.

"Nothing is moving at all," along the route that's vital for South Africa's exports of chrome, a key ingredient in stainless steel, said Barbara Mommen, owner at Coalescence, a cross border trade consultancy. There will be a "huge impact on trade efficiency and enormous cost to exporters and operators. And consequent losses to the regional economy."

An average 1,500 trucks mainly exporting chrome, but also coal, travel to Maputo's port along the highway daily, Ms Mommen said. Delays cost operators ZAR5,000 (US$298) a truck per hour, she said. That equates to as much as $14 million a day.

"We've got a huge crisis," said Ms Mommen. "Those sorts of losses are not easy to recoup."

The protests follow a strike by bus drivers in Maputo, Mozambique's capital, on Monday after diesel prices were increased by 11 per cent and gasoline by 4.4 per cent. The action ended after the government pledged to subsidise some fares.