Cape Town — The violence against foreign migrants living in South Africa spread to the centre of a major South African city on Tuesday as crowds reportedly numbering thousands gathered on the streets of Durban.

Reporters said police fired rubber bullets and stun grenades in an attempt to disperse the crowds. In the first signs that migrants could begin striking back at locals who have attacked them and looted their shops, they were reported to be arming themselves with baseball bats and machetes. In one area of Durban, they were reported to have tried to erect a barricade.

The state-controlled SA Broadcasting Corporation said foreign nationals retaliated when locals tried to loot their shops.

A reporter for Eyewitness News tweeted that a number of migrants were heard shouting: "If you want Boko Haram in this country, continue killing us."

The Sowetan said Durban's central business district was "under total lockdown" as police confronted crowds of locals and migrants.

Earlier, News24 reported that several people had died and thousands displaced in violence in Durban's apartheid-era black townships.

The news service said police were overrun on Monday night as groups of locals moved from shop to shop, looting the possessions of migrants operating in the KwaMashu township.

Until now, most attacks have taken place in the informal settlements and townships in the which the poorest South Africans live. Much of the violence in the past has been generated by a struggle for access to resources in those areas, with successful migrant business owners becoming the target of their local counterparts, as well as of opportunistic criminals.

The current outbreak of attacks follows remarks by Zulu King Goodwill Zwelithini at the end of last month, in which he was reported to have criticised foreigners for taking over South Africa's wealth.

Local news media quoted him as saying that "when you walk in the street you cannot recognise a shop that you used to know because it has been taken over by foreigners, who then mess it up by hanging amanikiniki (shabby goods)."

South Africa's Human Rights Commission is investigating his remarks.