The police have banned countrywide commemorative marches planned by church groups to mark the plight of thousands of people left homeless in the aftermath of the government's controversial Operation Restore Order.

United Nations estimates say more than 700 000 people were left without roofs over their heads when the government launched the operation, also known as Operation Murambitsvina (Clean the Dirt), destroying thousands of illegal structures in the country's major towns in May last year.

A spokesman for the Zimbabwe Christian Alliance (ZCA) told Reuters that the police had summoned pastors and ordered them to cancel weekend prayer meetings and a march in sympathy with victims of the blitz.

"We are likely to challenge that in the courts because prayer meetings and peaceful processions by churches should not require police permission," said Hussein Sibanda, ZCA spokesperson.

Human rights groups have planned eight weeks of meetings and marches to commemorate the crackdown that was condemned by the UN after it dispatched its representative, Anna Tibaijuka, to Zimbabwe to assess the impact of the demolitions.

Leading human rights activist Dr John Makumbe and university lecturer, was detained for about five hours on May 17, 2006, for apparently assisting rights groups in coming up with a programme to commemorate the demolitions.

NGO officials and journalists were on May 16, 2006, barred from entering Hopley Farm, a government holding camp on the outskirts of Harare after state security agents demanded that they produce official clearance letters.