Democratic Republic of Congo President Joseph Kabila

Pretoria - Members of a rebel Democratic Republic of Congo (DRC) group, accused of plotting to overthrow President Joseph Kabila's government while in South Africa, are challenging the validity of local foreign military assistance legislation.

The trial of the 20 alleged coup plotters was postponed on Monday in the High Court in Pretoria to Monday next week.

Strict security measures were maintained at court with heavily armed Task Force members in attendance.

Angry supporters of the group, who vowed to see that justice was done, were searched before being allowed to enter the courtroom.

This was for the state to prepare legal argument on a constitutional challenge to the validity of the SA Regulation of Foreign Military Assistance Act.

Some of the accused also intend launching a legal challenge against the South African court's jurisdiction to try them here on charges of plotting to murder Kabila and top-ranking members of his government in the DRC.

The court was told last week that certain of the accused were disputing the legality of the police trap that resulted in their arrest.

They claim the trap, set by officers of the Hawks, went much further than creating the opportunity to commit a crime.

Prosecutor Shaun Abrahams said the State was prepared to present legal argument on some of the issues, but it would be extremely irresponsible to rush into legal argument about the constitutional issues.

Judge Billy Mothle warned the accused and their advocates to raise all preliminary issues before Friday this week as he did not want any further delays in the trial.

He said the accused had already been in custody for 15 months and their trial should commence as soon as possible.

Mothle ruled that the charges would first have to be put to the accused on Monday next week and they would be asked to plead before the legal challenges could be dealt with.

Three of the accused were taken on Sunday to receive medical treatment after complaints that they had been assaulted in prison, were kept in their cells 23 hours per day and that prison authorities were treating them inhumanely.

Judge Mothle last week ordered the police to investigate the allegations and report back to the court.

Nineteen of the men, including US-Congolese citizen James Kazongo, were arrested on February 5 last year in a police raid in Limpopo.

The group's alleged leader Etienne Kabila, who claims to be the DRC president's half-brother, was arrested in Cape Town three days later after handing himself over to the police.

The State alleges the group were members of a dissident organisation in the DRC known as the Union of Nationalists for Renewal and were dissatisfied with the current leadership of the DRC government under President Kabila's leadership.

They face charges of contravening the SA Regulation of Foreign Military Assistance Act by engaging in mercenary activity and contravening the local Riotous Assemblies Act by conspiring to murder President Kabila and 15 top members of his government.

The State alleges the group between September and February last year met with under-cover members of the Hawks on several occasions.

They allegedly recruited two of the officers and others to provide specialised military training to the group and to procure large numbers of assault rifles, grenades, machine guns, air-to-air missiles, satellite phones and two-way radios for them.

The State alleges the group's mercenary activities in South Africa had been aimed at a coup d'etat in the DRC to unseat the country's government.

It is further alleged that the group had conspired to murder Kabila and several DRC government officials, including the Chiefs of the DRC Air Force and Navy, the National Intelligence Director, the Governor of the Central Bank and the Minister of Interior.