Two protests are causing disruptions in Soweto and Pretoria on Tuesday afternoon.
In Soweto, officers are on high alert in Mofolo North as hundreds of people protest over power cuts in the area.
Residents blocked the main road with rocks, rubble and burning tyres, complaining about what they claim is a four-week power cut.
Protesters want Eskom and the City of Johannesburg to urgently resolve the issue.
A woman said the power utility told the community one of its transformers is broken and it's unable to meet their demand for electricity.
"They don't have a solution but they said they could install prepaid [meters]. They can't do that because most of us aren't working so we won't be able to buy electricity."
Police are monitoring the situation as residents continue to burn tyres and block access roads between Mofolo, Dube and Meadowlands.
Officers are also keeping a close eye on informal traders in the Pretoria CBD on Tuesday afternoon.
Authorities say the demonstration by informal traders in the area is illegal.
Metro police officers from the City of Tshwane said 500 traders gathered this morning with the intention to march to the Union Buildings.
But it appears demonstrators are trying to head to the metro council's offices instead.
Tshwane Barekisi Forum's Mary Ngema said the traders want to hand over a memorandum to Mayor Kgosientso Ramokgopa, calling for an end to police victimisation.
"We want the metro police to stop harassing the traders."
Both the council and the forum denied claims the protest was marred by violent clashes, saying the march was peaceful.
According to a shop owner in the city centre, some businesses were closed following warnings.
"This morning, businesses didn't want to open because the police went to some people in the area and told them to remain closed as they can't guarantee their safety."