Their call came just hours before another crash left 21 people injured - 19 of them seriously - when a bus left the road and crashed into a river in Eastern Province.

The BBC's Jane Standley: "The wreckage of the bus has been cleared"

The latest accident is the sixth in a series of major bus crashes in South Africa that have claimed 59 lives in just one week.

"I think we do have a problem with regulation," said Jeremy Cronin, chairman of Parliament's transport committee.

He said rules would be reviewed next year, and added what is obvious to drivers on South Africa's highways - traffic enforcement is sparing at best.

"Figures suggest 8,000 traffic officer posts are currently vacant," he said.

Paul Swart, a spokesman for the opposition Democratic Party, called for improved policing, more frequent roadworthy tests and limiting the number of hours bus drivers spend at the wheel.

"It is clear urgent action is needed," he said.

The spate of deaths began last Saturday when 15 people were killed when a bus went off a highway in foggy weather and crashed into a tree at Kokstad, a town in KwaZulu-Natal province in eastern South Africa,

Many of the victims were elderly

On the same day, two buses, one carrying a school cross-country running team, collided 155 miles south of Johannesburg, killing six people. Twelve people died when a tourist bus and a truck collided last Wednesday in Western Cape province.

Monday's crash happened on steep, narrow and unmarked Long Tom Pass near Lydenburg, a popular stop in South Africa's Mpumalanga province.

The South African Government has vowed to halt the deaths and transport minister Dullah Omar is planning to meet with bus company representatives on Thursday.

A spokesman said: "Mr Omar was shocked by the news and a meeting with the country's bus operators is now a priority.

"The minister wants to see what precisely needs to be done to bring down the high rate of accidents."

The government has already launched an "Arrive Alive" ad campaign, urging drivers to avoid speeding and to stop and rest when they are sleepy.