More than 10,000 Mozambicans have fled home from South Africa to escape anti-foreigner violence that has killed at least 42 people and left more than 30,000 homeless.

Their escape comes as President Thabo Mbeki ordered the armed forces to quell the unrest for the first time in the country since the end of Apartheid.

Air force helicopters were deployed to back up police in Johannesburg's Alexandra township over fears the crisis could massively destabilise Africa's largest economy.

Mean streets: A South African policeman patrols the Ramaphosa settlement in Johannesburg as Thabo Mbeki ordered the army to stop the violence

Armed mobs, who have forcefully driven thousands of immigrants from their homes before looting and torching their shacks, accuse them of stealing jobs and fuelling crime.

The violence, which has since spread from Johannesburg to Durban, has also seen the return of necklacing – the brutal practice of filling a tyre with petrol and throwing it over the victim's neck.

The deadly method has not been seen since the Apartheid era when black South Africans used it on “collaborators” with the white minority rulers.

Fears of attacks have led to thousands of immigrants, mainly from Zimbabwe and Mozambique, fleeing the country.

Emergency: A refugee camp outside Primrose Police Station, Johannesburg, where about 1,000 people now live

Mozambique's Deputy Immigration Director Leonardo Boby today said: "10,047 returned home in buses provided by the government.

 "The number is likely to increase in the next days as long as violence unfolds in South Africa.

The deputy leader of the ruling African National Congress, which ousted Mbeki as party leader in December, criticised the police delay in responding to the violence which erupted in Alexandra township on May 11 and spread rapidly.

"The delay encouraged people in similar environments to wage similar attacks against people who came from our sister countries on the continent," Kgalema Motlanthe said.

Fear: A Zimbabwean resident from the Ramaphosa settlement, Johannesburg, cries after her shack was looted

"We are confronted by one of the ugliest incidents in the post-apartheid era."

 Mr Motlanthe also said the violence was an assault on the values of South Africa's democratic society.

 He is a close ally of ANC leader Jacob Zuma, who defeated Mbeki for the party leadership.

The attacks on African migrants have increased political instability at a time of power shortages and disaffection over Mbeki's pro-business policies.

Victim: A man from Malawi lays wounded today as a baying mob encircle him in the Reiger Park settlement outside Johannesburg