South African police have arrested four right-wing extremists, suspected of having weapons and planning attacks on undisclosed targets, a spokesman said Monday.After a nearly two-year investigation, police arrested four men, "believed to be right-wing extremists, suspected of acts of terrorism,” according to police spokesman Brigadier Billy Jones.During a raid, police said they uncovered evidence supporting the investigation on their premises.Mr Jones told AFP the plot was not linked with the ruling ANC’s political conference under way in the city of Bloemfontein."We are not linking this to the ANC conference. The investigation is taking place at several points across the country,” he said."Four people were arrested... not linked to the conference at all. . . . Those people were arrested in different places in the country.”Local media claimed that the plot was targeting the African National Congress’s five-yearly leadership conference in Bloemfontein.Security has been extremely tight around the conference, with razor wire thrown up around a perimeter guarded by armed police.High treasonOnly a few pre-screened vehicles are allowed to enter what is normally the campus of the University of the Free State.The Free State province is historically a hotbed of Afrikaner nationalism.Since the fall of the white-minority apartheid government in 1994 numerous right-wing groups have turned to violence.In August 20 people were convicted of high treason in connection with a plot to kill Nelson Mandela and drive blacks out of the country.The "Boeremag” organisation had planned a right-wing coup in 2002 to overthrow the post-apartheid government.Dozens of people were injured and one person killed in blasts that shook the Johannesburg township of Soweto in October 2002.South Africa’s opposition Democratic Alliance condemned the alleged plot and appeared to link it to the ANC party meeting."It appears some on the lunatic fringe of our politics still do not respect the rights of all parties to exist. They must face the full force of the law.”