The election was rigged and therefore null and void

Anderson Mazoka

Official results gave Mr Mazoka 27% of the vote against 29% for Mr Mwanawasa but both local and foreign monitors said there had been widespread irregularities.

"It should be determined and declared that the electoral process was not free and fair and that the election was rigged and therefore null and void," he said in his petition.

Legitimate

Christon Tembo, Godfrey Miyanda, Tilyenji Kaunda and Reverend Nevers Mumba, who all stood in the elections, said they backed Mr Mazoka's challenge and would help gather evidence in the case.

But President Mwanawasa denied that there had been anything untoward.

"I am the legitimately elected president of Zambia. Those who wish to litigate can do so, and I stand ready to defend myself and prove their futility," he told Reuters news agency.

Mwanawasa says he has nothing to fear

The election was marred by violent street protests by opposition supporters and Mr Tembo had threatened more unrest when the official results

But for the moment, the opposition is sticking with the legal process, as well as hoping that their overall parliamentary majority will enable them to make life difficult for Mr Mwanawasa.

The police raid on the UPND office follows last week's arrest of five suspected opposition supporters, accused of setting off a tear gas grenade in a supermarket.

"They conducted the search in our presence but found nothing. They are just hunting our leaders with fake investigations," said Love Mtesa.

On Tuesday, a group of men tore the clothes off several Lusaka women, saying they were improperly dressed.

They said they were implementing a new presidential decree but this was denied by Mr Mwanawasa.