South Africa will not tighten border controls despite many illegal immigrants entering the country, Home Affairs Minister Nosiviwe Mapisa-Nqakula said on Tuesday.

"Economic migrants will always find a way of moving into areas where they shouldn't be," she told reporters in Johannesburg.

"You are not going to be able to prevent that."

The worst thing South Africa could do was "to go back to the past where we had electric fences meant to restrict people".

She was speaking at a media briefing on immigration logistics for the 2010 Fifa World Cup, and how African countries would be accommodated to attend the event.

Referring to Beit Bridge, South Africa's border with Zimbabwe, she said it was originally developed in a manner that "allows little movement between South Africa and the rest of the continent.

"But we are talking of free movement of people," said Mapisa-Nqakula.

Tighter border controls would "actually encourage illegal migration."

"Our emphasis is on facilitation of movement rather than tighter border control... then you know who is in the country and what they are doing."

There are no official numbers available on illegal immigrants in South Africa, but some estimates are as high as two million, a situation exacerbated by the socio-economic and political crisis in Zimbabwe.