Zimbabwe - The entire leadership of Zimbabwe's union for farm workers has gone underground after a series of raids, arrests and threats against them, lawyers said on Sunday.

The raids followed a documentary which the union had produced exposing violent abuse of workers on white-owned farms seized by President Robert Mugabe's backers, lawyer Trust Maanda said.

The documentary, titled The House of Justice, was released last year after years of recording the lawless take-over of nearly all the country's white-run commercial farms since 2000.

Maanda confirmed that Gertrude Hambira, secretary-general of the General Agricultural and Plantation Workers Union of Zimbabwe (Gapwuz) was in hiding since Wednesday.

She had been interrogated that day for two hours at the police national headquarters by 17 senior officers of the Joint Operations Command (JOC), which combines the country's military, police and intelligence service and which is known to direct the political strategy of Mugabe's Zanu-PF party.

Gapwuz officials said Hambira was told she would go behind bars for the documentary, which showed gruesome images of farm workers murdered and tortured by Mugabe's militias.

Lawyers say it is unprecedented and illegal for the JOC to carry out interrogations and issue threats.

A second raid was carried out on Hambira's office on Friday in which two officials were arrested, but released after a few hours. Two more have been ordered to police for interrogation on Monday, Gapwuz officials in hiding said.

London-based Amnesty International last week denounced the latest in a series of Zimbabwean human rights violations that continue despite the formation of a power-sharing government of national unity in February 2009 by Mugabe and pro-democracy leader Morgan Tsvangirai.

By SAPA