The state-owned Herald newspaper quoted Mugabe as telling supporters at a rally on Thursday that the veterans had asked him if they should be ready to fight.

"They came to my office after the (disputed March 29) elections and asked me: 'Can we take up arms?'," Mugabe said.

The Herald said Mugabe told the war veterans that he did not want the country to go back to war but said Zimbabwe would never be ruled by the opposition MDC, which won the first round.

"It will never happen that this land which we fought for should be taken by the MDC so that they can give it back to our former oppressors, the whites," the paper quoted him as saying.

Movement for Democratic Change leader Morgan Tsvangirai, human rights groups and Western powers accuse Mugabe of unleashing a brutal campaign to win the run-off.

Tsvangirai says 66 of his followers have been murdered but former guerrilla leader Mugabe, who has ruled since independence from Britain in 1980, blames the MDC for violence that has caused widespread international concern.

Earlier, the MDC said Zimbabwean police impounded two campaign buses used by Tsvangirai in the latest action against the opposition leader in the election campaign.

Tsvangirai, who has been detained four times in the past week and has had his own vehicle confiscated, would continue the campaign, MDC spokesman George Sibotshiwe said.

HIGH COURT BID

The third most senior MDC leader, Tendai Biti, was arrested on his return from abroad on Thursday and faces a treason charge which could carry the death sentence.

His lawyers said on Friday they have still not been given access to him. An urgent application asking the High Court to intervene was made on Friday, lawyer Lewis Uriri said.

The MDC said it was very concerned about Biti 24 hours after he was arrested.

"The MDC has dispatched a team of lawyers and human rights defenders to every possible police station in Harare in an effort to secure his whereabouts. The MDC is deeply worried about the welfare of the secretary-general," the party said.

Also on Friday, a regional human rights group said Zimbabwean police had ordered domestic non-governmental aid groups to cease operations.

The South African Litigation Centre (SALC) said police had ordered several NGOs to close, including human rights groups and the Zimbabwe Women Lawyers Association.

The move followed a ban last week on international humanitarian groups working in Zimbabwe, which faces a chronic food and economic crisis.

U.S. humanitarian affairs chief John Holmes said on Thursday the situation was deteriorating rapidly. He called it "very worrying and very serious ... with up to 4 million people in need of humanitarian assistance".

SALC director Nicole Fritz said: "There simply aren't enough lawyers left to try to challenge all these unlawful actions. And now the NGOs are being forced to close. The Zimbabwean government seems intent on ensuring that there simply will be no possible redress left to ordinary Zimbabweans."

Washington has called for urgent U.N. Security Council talks on Zimbabwe. But diplomats said South Africa, supported by China and Russia, opposed Security Council involvement.

Mugabe and ZANU-PF were defeated in March for the first time since independence in 1980 but Tsvangirai failed to win the presidential vote outright, necessitating a second round.

A group of prominent African leaders joined the calls for an end to violence in Zimbabwe, once a regional bread basket but now suffering economic collapse.

"It is crucial for the interests of both Zimbabwe and Africa that the upcoming elections are free and fair," former U.N. Secretary-General Kofi Annan and 39 former African heads of state and civic leaders said in an open letter on Friday.

The Southern African Development Community, a grouping of 14 nations including Zimbabwe, has sent a team of election monitors to Harare. Observers from Western nations critical of Mugabe's government are not being allowed into the country.