Anti-immigrant violence has spread to South Africa's second largest city, Cape Town, where mobs attacked Somalis and Zimbabweans and looted their homes and shops, police said on Friday.

Hundreds of African migrants were evacuated overnight from a squatter camp near Cape Town, the hub of South Africa's prized tourism industry. Somali-owned shops also were looted in Knysna, a resort town on the southwestern coast.

"We don't know the exact number of shops looted and burnt, but it's a lot," said Billy Jones, senior superintendent with the Western Cape provincial police. He added that one Somali died overnight but it was unclear whether the death was linked to the attacks.

At least 42 people have been killed and more than 25,000 driven from their homes in 12 days of attacks by mobs that accuse African migrants of taking jobs and fuelling crime. More than 500 people have been arrested.

The unrest began in Johannesburg area townships but has spread to other provinces. Authorities warned more attacks were expected over the weekend and said they would seek additional assistance from the military if necessary.

Troops have joined police in operations in Johannesburg's seething shantytowns. President Thabo Mbeki approved army intervention to quell unrest that has threatened to destabilise Africa's largest economy.

The South African currency fell sharply earlier this week on the back of the violence. The rand was slightly firmer on Friday at 7.63 to the U.S. dollar.

The violence comes amid power shortages and growing disaffection over Mbeki's pro-business policies. Soaring food and fuel prices helped push tensions between poor South Africans and immigrants to a breaking point. The attacks have also sent a chill through the business community.

Officials in the tourism industry, a cornerstone of the economy, are worried overseas visitors will avoid the country. A number of Western governments have issued travel warnings for South Africa, and tour companies report rising cancellations.

Nearly one million South Africans earn their living from tourism, which accounts for 8 percent of the country's GDP. The country is hoping to draw an additional half a million tourists for the 2010 soccer World Cup.

MIGRANTS HEAD HOME

South Africa had attracted millions of African immigrants with the prospect of work in its booming economy and an immigration and asylum policy that was considered one of the most liberal in the world. That reputation is now in tatters.

Thousands of African migrants have chosen to return home.

Mozambique said more than 10,000 migrants and their families had left South Africa since the violence broke out, and officials in the Portuguese-speaking southern African nation expected the number to swell in the coming days.

Zimbabwe's opposition leader Morgan Tsvangirai said on Thursday that officials in his Movement for Democratic Change would help arrange transportation for refugees who wanted to go home to Zimbabwe, which is mired in a deep economic crisis.

Tsvangirai is trying to unseat President Robert Mugabe in a June 27 presidential run-off vote.

There are an estimated three million Zimbabweans in South Africa, making them the biggest immigrant group.

Some Zimbabweans are willing to go home despite Zimbabwe's hyperinflation, shortages of food, and an upsurge in political violence since disputed elections almost two months ago.

Others, however, are waiting it out in overcrowded shelters.

Bishop Paul Verryn of the Central Methodist Church in Johannesburg, where many Zimbabweans have fled, said tensions were high among refugees, who still feared further attacks.

"One senses a profound anxiety and fear," Verryn told the South African Broadcasting Corp.