As the protest spread to a second region, with other areas also considering action, Morgan Tsvangirai, president of the Movement for Democratic Change, backed the landowners and threatened strike action in "solidarity" with their employees. His intervention came after another white farmer was severely injured by squatters, when a mob of 40 set upon him with sticks and clubs.

With 237 farmers now on strike, Tim Henwood, the president of the Commercial Farmers' Union, said the protest could spread nationwide because normal operations were becoming "impossible". He petitioned Mr Mugabe to halt the land invasions, which commenced in February, and began a fresh legal attempt to end his members' ordeal.

Farmers around Karoi, 150 miles north-west of Harare, began their strike at 6am yesterday. Irrigation systems were switched off and their 27,000 workers sat idle, although they will be paid for as long as possible. The protest was joined by 57 farmers in neighbouring Tengwe. Alan Parsons, one of the striking landowners, said: "We want law and order back in our country.

"That's what this is about. We can't continue in this state of anarchy any longer." He said a nationwide strike was on the cards. Some of Karoi's shops and garages closed in solidarity with the landowners after Mr Tsvangirai called the farmers' action "justified". He said: "If this lawlessness continues, the protests may spill into the urban areas, where workers will be forced to take action in solidarity with farm workers who now live under constant fear of losing their lives or jobs." Mr Tsvangirai is a former secretary-general of the Zimbabwe Congress of Trade Unions, which has close ties with the MDC.He led a series of national strikes in 1997 and 1998, and senior figures in the MDC believe such action is necessary again. A member of Mr Tsvangirai's executive said: "What we need is a general protest, covering every industry, until we return to the rule of law. I think it will happen soon."

Beleaguered farmers, who have lost all confidence in the police, were still shocked yesterday by the attack on Mr Brand, one of the striking farmers, outside his gates at Gremlin farm, Karoi. He said: "They came and said they wanted to take my farm. I turned to go back to my security gate and that's when they started beating me. They hit me with sticks until I dropped to the ground." Mr Brand was rescued by fellow farmers and rushed to Chinhoyi hospital, where he was treated for a fractured arm, severe bruising and lacerations to his head and right ear. He told them the squatters had "got into a frenzy and wanted to take vengeance on somebody".

Farmers are reaching the end of their patience after an ordeal that has lasted for almost six months. Mr Henwood gave the CFU's first warning of national action. He said: "In the interests of the safety of our members and their workers it may soon become impossible for farming operations to continue nationwide. "This drastic action will have a serious impact on the economy of Zimbabwe but will be a small price to pay to prevent further loss of life." Mr Henwood begged the president "to intervene in bringing to an end the perils faced by all those involved in commercial farming".

The CFU asked the High Court to order the police to evict the squatters and act against violence. Judges have already granted this request twice, but their orders have been ignored. Few believe that the third legal attempt to solve the crisis will meet with any more success.