"We, together with Ekurhuleni metro police department, are on high alert for any incidents of violence during the truck drivers' strike," said spokesperson William Ntladi.
He said a truck was stoned by protesters in Kempton Park on Wednesday, but no injuries were reported.
In Germiston, on the M2 and Refinery road, protesters stopped a truck with three occupants.
"The two assistants in the truck driver were hospitalised after being assaulted by the protesters, but the driver managed to escape and opened a case … [with the] police," Ntladi said.The truck was set alight.
About 20 000 workers in the freight transport sector are on strike over wages. Their unions have reverted to a 12% pay demand after rejecting a lower offer tabled by employers on Tuesday.
The Road Freight Employers' Association had proposed a staggered increase of 8.5% effective from March, and a further 0.5% from September next year – resulting in a 9% increase in total.
Workers embarked on a protected strike on Monday after wage negotiations deadlocked.
The four unions involved are the South African Transport and Allied Workers' Union, the Professional Transport and Allied Workers' Union South Africa, the Transport and Allied Workers' Union of South Africa and the Motor Transport Workers' Union.
Striking truck drivers also set alight vehicles and intimidated a driver in Cape Town and Durban, police said.
A driver and his two assistants were hospitalised after being injured while trying to escape angry protesters.
The driver collided with a car, then hit a tree during the altercation. He sustained serious head wounds, while his two assistants were slightly injured.
In Cape Town, striking truck drivers set alight two trucks in Nyanga.
Investment Solutions economist Chris Hart told the New Age on Thursday South Africa might slip into a second recession if the transport strike was protracted. – Sapa