About 300 people went on an illegal march in Pretoria on Thursday in a bid to get their jobs back, Tshwane metro police said.
"These people are contract workers, working on a waste management contract that was terminated last year," spokesman Isaac Mahamba said.
Mahamba said they gathered illegally at Prince's Park around 10am and marched to the municipal offices. They wanted management to address them.
When police arrived on the scene, the strikers threw stones at them. Water cannons were used to disperse them. No one was injured, and five people were arrested for public violence.
Comment from the municipality could not be immediately obtained.
Mahamba said the strikers should voice their grievances using the right channels.