South African Defence Minister Mosiuoa Lekota has said that a small extremist white group in the armed forces and police could be behind the bombing in Soweto

He told Reuter news agency that he believes they are seeking to destabilise the government.

About two million people live in sprawling Soweto

So far no one has been arrested or claimed responsible for the bomb attacks that killed a woman and injured her husband.

But major airports have beefed up security. Cars entering Africa's biggest airport in Johannesburg were being searched on Thursday.

Nine bombs exploded, one after the other, from late on Wednesday night across the sprawling township.

"They are a racially oriented group. They want to achieve a race war," Mr Lekota said.

"It certainly does not represent the majority of Afrikaners... but a residue within the South African National Defence Force [SANDF] and the South African Police Service."

Blasts

South Africa's President Thabo Mbeki has condemned the bomb attacks and warned that it could be the start of a terrorist campaign.

Several of the explosions targeted railway lines linking Soweto to Johannesburg, leaving busy commuter routes in chaos. Another explosion ripped through a mosque, tearing apart one of its walls.

On Wednesday morning, police announced a further blast had occurred at a temple in Bronkhorstpruit, a town east of the capital, Pretoria. It is unclear if the blast is linked to the Soweto explosions.

Police Commissioner Jackie Selebi is reported as saying that two white men were seen acting suspiciously in Soweto shortly before the explosions.

A BBC reporter says the attacks were well co-ordinated by people who probably had military training.

Recently a group of 15 white extremists went on trial, accused of plotting to overthrow the state. Two more have now been arrested over the plot. A total of three are reported to have links to SANDF.

Soweto Police Superintendent Richard Luvhengo said it was the first such incident in memory in South Africa's biggest township,

It is also the worst bombing spree, outside of Cape Town, since one by white right wingers ahead of the first all-race elections in 1994.