Extra police officers were deployed to the Philipi district of Cape Town, a city that suffers from regular gang violence and armed clashes between rival criminal groups.
"We have deployed teams comprising specialist detectives, high-risk units and intelligence operatives," police spokeswoman Novela Potelwa told the News 24 website.
"We already executed search operations that are set to continue throughout the day. The police are doing their best to arrest those responsible."
Tens of thousands of people live in informal shack settlements in Philipi, located in the notoriously crime-ridden Cape Flats area of the city.
Four people were shot dead at an informal "shebeen" bar on Friday evening, with three other bodies found by police nearby. Another four more people were killed elsewhere in the district.
"Regardless of the circumstances, these mass murders -- related or not -- are criminal acts which must be punished using the full might of our law," party spokesman Zizi Kodwa said in a statement.
"Criminals live amongst our communities, they are harboured by us and until society stands as one against this scourge, it will not be defeated."
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