In three simultaneous raids carried out on farms and smallholdings in Gauteng, Northern Cape and Limpopo yesterday, Hawks officers seized laptops and files said to contain detailed plans and photographs outlining the alleged assassination plot in Mangaung.

The killings were allegedly to have happened on Monday, the second day of the ANC's elective conference. The documents are said to describe the planned robbery of gun shops, military bases and police stations. They detail how the suspects would allegedly use mortars, sniper rifles, machine guns and armoured vehicles in the assault, said to have targeted Zuma, the ANCs newly elected executive and conference delegates.

Yesterday's raids came after similar raids over the weekend in which police arrested Mark Trollip, 48; John Martin Keevy, 47; Johan Hendrik Prinsloo, 49, and Hein Boonzaaier, 51. The four appeared under heavy police guard in the Bloemfontein Magistrate's Court yesterday on charges of high treason and terrorism. As they appeared, police yesterday followed up on information on suspected weapons caches thought to contain hand grenades and mortars, but no caches were found.

Prinsloo and Boonzaaier are listed as executive members of the Federale Vryheidsparty, registered as a political party with the Independent Electoral Commission earlier this year.

The investigation, according to police sources, is looking at the suspects' alleged links to other extremist groups. A police source said "huge" information was gained from raids in Prieska, Modimolle and Springs, where the laptops were seized.

The source said officers discovered a suspected paramilitary training camp in Modimolle - where camouflage uniforms, military insignia and pellet guns used to train recruits were seized.

The plans, he said, showed how many people were needed for the attack, where weapons would be obtained and how police and soldiers responding to the assault would be fought off.

"Information shows the suspects - who are businessmen and farmers - have support from several quarters. Investigations are looking at who is supporting them and what kind of support they had."

Prosecutor Shaun Abrahams alleged the four, who were remanded in custody, and other right-wing extremists had worked on their "deadly" plan since January.

The case was postponed to January 8.