Robert Mugabe is preparing to defy international pressure and launch a systematic crackdown in Zimbabwe aimed at reversing his defeat in the presidential election two weeks ago, according to dissident policemen who have been briefed on his plans.

Through an intermediary, the policemen told The Independent on Sunday that they have been ordered to be ready to deploy today or tomorrow. With their ranks swollen by so-called "war veterans" given police uniforms, they would take over constituency "command centres" used in the 29 March elections.

Two weeks ago the ruling Zanu-PF party not only lost its majority in the House of Assembly, but, in the presidential contest, Mr Mugabe is believed to have finished well behind Morgan Tsvangirai, leader of the opposition Movement for Democratic Change (MDC).

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The growing crisis over the government's failure to release the election results, coupled with rising violence in rural areas where the MDC did well, has reinforced fears of a crackdown. Mr Mugabe has also defied international pressure to declare the result, spurning a regional summit on Zimbabwe's problems called yesterday by the President of neighbouring Zambia.

On Friday, police banned all political rallies, a move initially thought to be aimed at an MDC protest meeting in the capital Harare today. A police spokesman said the force did not have enough officers to handle rallies because many were still guarding ballot boxes or preventing post-election violence. But it appears the order may also have been issued to give the police time to move into position around the country. Once they are deployed, opposition parties believe, the government could announce the presidential result and the date of the second round, claiming no candidate won an overall majority. This would also forestall the MDC's High Court action demanding the immediate release of the results, on which a judge has promised to rule tomorrow.

The dissident policemen said that "war veterans" – in reality Zanu-PF enforcers – would be given police uniforms, and, for the first time, police numbers, making it impossible to distinguish them from regular officers.

In rural constituencies, the policemen said they had been told their role would be to campaign openly for Mr Mugabe. Some areas would be closed altogether to outsiders. "This is a national plan," they told the intermediary. They added that the "war veterans" had been recruited to act as watchdogs over any policemen reluctant to carry out orders.

President Thabo Mbeki of South Africa met Mr Mugabe in Harare yesterday before going on to Zambia, but said there was "no crisis" in Zimbabwe and called for patience. Yesterday, Gordon Brown called for the election results to be published "immediately".