Civil rights group AfriForum will launch a legal challenge against an investment agreement to be signed with Zimbabwe this week, a spokesperson for the group said on Monday.

The agreement, which is to be signed in Harare on Friday, aims to protect current and future investments of South Africans in Zimbabwe, but "expressly excludes" the investments of South African farmers affected by President Robert Mugabe's land programme, AfriForum legal representative Willie Spies said.

"If the signing ceremony were to proceed, an application for an interdict against it will be submitted to the North Gauteng Supreme Court in Pretoria on Friday," Spies said.

AfriForum has provided Trade and Industry Minister Rob Davies with a legal opinion that the proposed agreement is in contravention of the South African constitution, several international legal principles and existing court orders of the High Court in Pretoria.

Mugabe's land programme was "racist"

The farmers are being represented by Louis Fick, a farmer from Chinoye in the east of Zimbabwe.

Fick is a South African citizen and has been farming in Zimbabwe since 1993.

He was one of 79 farmers who brought a successful legal action at a tribunal of the Southern African Development and Economic Community in November 2008.

The tribunal found that Mugabe's land programme was "racist and illegal and had to be terminated", according to Spies.

"Mugabe however did not pay heed to the tribunal's findings and stepped up his programme."

Had to "get rid of" all his livestock

After the finding, Fick's farm was occupied by a group, under the instruction of a senior official of the Zimbabwean Reserve Bank, a Mr Mashiringwani.

"This group time and again prevented Fick from caring for his livestock.

"This caused the deaths of 200 pigs, as well as other livestock, due to starvation and thirst."

Fick recently had to "get rid of" all his remaining livestock on the farm.

Fick was arrested and detained for a night in the police cells at Chinoye after failing to comply with an official notice ordering him to vacate his farm.

He has since been charged and will soon stand trial on a charge of disrupting the land reform programme.

If he is found guilty of the "misdemeanour", he may be sentenced up to two years imprisonment in a Zimbabwean jail.