Cape Town — South African troops will move into flashpoints in the country's economic heartland to help police end attacks on migrants from other parts of Africa.

President Thabo Mbeki's office annnounced late on Wednesday that he had approved a police request for help from the South African National Defence Force in stopping attacks on foreign nationals in Gauteng Province.

More than 20 migrants have been killed and thousands driven from their homes since the violence began in Alexandra Township in Gauteng last week.

The well-informed military correspondent of the Gauteng newspaper, Beeld, reported earlier today that the defence force chief, General Godfrey Ngwenya, had transmitted a police request for help to Mbeki's office on Monday. The army was ready to act, the report said, but had to await Mbeki's decision. South Africa's constitution requires presidential approval for the deployment of the army in support of police.

The newspaper quoted military sources as saying the defence force's primary aim would be to mount a show of force to make it easier for the police to end the violence. The police had asked for troops, armoured vehicles and aircraft. Military medical services would also be deployed.

Since liberation, troops have rarely been seen on the streets of South Africa. Deploying them in black residential areas is controversial, associated in the minds of many with the final days of the struggle against apartheid. In the 1980s, apartheid leaders mobilised their army against anti-apartheid activists who were responding to calls from African National Congress leaders in exile - Mbeki prominent among them - to make the areas "ungovernable".