South African police investigating an alleged plot by white extremists to topple the government have found a cache of 26 bombs.

The devices, similar to pipe bombs, were found in the farming area of Keimoes in Northern Cape province, along with other unnamed military material, the police have said.

We feel there is a direct link to the plan to overthrow the government

Sally de Beer, Police spokeswoman

Twenty white men are due to stand trial on charges of treason next May.

A shadowy right-wing group has claimed responsibility for last month's series of bombings in the black township of Soweto, which killed one woman and injured her husband.

The "Warriors of the Boer Nation", which may be linked to the Boeremag (Afrikaner Force), said the Soweto bombings "are the beginning of the end for the African National Congress (ANC) government".

The group also demanded the release of those held on treason charges.

'Race war'

In another raid in Umtata, Eastern Cape, police say they have arrested a man in possession of illegal machine guns and hundreds of rounds of ammunition.

Police spokeswoman Sally de Beer told the BBC's Focus on Africa programme that Northern Cape, where the bombs were found, was one of four or five provinces where white extremists are active.

"We feel there is a direct link to the plan to overthrow the government," she said.

Police have released the names of six men they are looking for in connection with the alleged plot and the Soweto bombings.

They are believed to be Boeremag members.

South African Defence Minister Mosiuoa Lekota has said he suspects those behind the Soweto bombings are former members of the army and police attempting to start a "race war".

"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," he said.