Police returned in force to crack down on counterfeit goods and crime in the Johannesburg CBD on Wednesday.

Spokesperson Brig Mathapelo Peters said the police were conducting a raid after closing off Von Weilligh and Rahima Moosa streets.

"We are raiding the buildings. We are confiscating counterfeit goods. We also arrested undocumented foreign nationals," said Peters.

Peters would not say what type of goods were confiscated and how many foreign nationals had been arrested.

Reporters on the scene shared footage of guns and ammunition - including an automatic rifle - seized in one of the buildings.

Johannesburg mayor Herman Mashaba said in a tweet that at least 30 foreign nationals had been detained.

Police and metro police were pelted with rocks and bottles during similar raids last week in the CBD.

Police said they made a tactical decision to withdraw during the street battle to avoid a "bloodbath" should they be forced to defend themselves with live ammunition.

This is a developing story.