Thursday's incident came as the Zimbabwe government moved to indefinitely suspend all aid work, a source with a national NGO said on condition of anonymity. Notices have been sent to aid groups informing them of the decision, the source said.

 

The confrontation at the roadblock, which occurred after what the government described as a gathering at the home of an opposition supporter, drew strong reactions from Britain and the United States.

 

"We are going to raise this at the Security Council ... and I sincerely hope that this time the Security Council does not consider the mistreatment of diplomats to be an internal matter for Zimbabwe," US Secretary of State Condoleezza Rice said.

 

The Council later "expressed concern" over the incident during consultations and urged "respect of the Vienna Convention, in particular protection of diplomats and property," Jeff Delaurentis, a minister-counsellor at the US mission to the UN, told reporters.

 

British Foreign Secretary David Miliband condemned the detention of the diplomats as "a serious incident."

 

Miliband said that the British party, consisting of one diplomat and three visitors, had been travelling around the country on "the normal business of diplomacy" when they were stopped at a roadblock.

 

The convoy of three vehicles was initially stopped at a checkpoint in the Bindura region before making a getaway and then later pulled over again, US embassy officials said.

 

"The police forced them (the diplomats) off the road and fortunately we had a good driver," US ambassador to Zimbabwe James McGee told reporters.

 

"They spiked our vehicle and slashed the tyres. The military came in, war vets came in and they threatened to burn my people," he said, referring to hardline supporters of President Robert Mugabe, who is currently in Rome.

 

"They were finally all released although they badly beat up our local driver. Fortunately all of them are now back."

 

The Zimbabwe government said it was "outraged" over the diplomats' actions, adding that they had been involved in a "commotion" at the activist's home.

 

"The British and American diplomats had gone to a house in Bindura where they addressed a gathering. There was commotion and police were called in," Deputy Information Minister Bright Matonga told AFP.

 

"When police arrived they fled and then they were stopped at a roadblock on the way.

 

"When they refused to disembark following orders by the police, police then deflated the tyres of one of the vehicles."

 

Asked for the identity of the person who lived in the house, Matonga said he was a member of the opposition Movement for Democratic Change (MDC).

 

Zimbabwe's top diplomat in London was summoned to the Foreign Office to explain what happened, but a spokeswoman for the ministry declined to give details on the exchange when contacted by AFP.

 

Miliband said the Zimbabwean ambassador would be told that the world is continuing to watch Zimbabwe and that the safety of diplomatic staff was paramount.

 

The incident highlighted the need for international monitors for the June 27 run-off presidential poll between Mugabe and opposition leader Morgan Tsvangirai to ensure it is free and fair, he added.

 

"The message that needs to go out today is a very strong one -- that the argument in Zimbabwe today is not between Zimbabwe and Britain, it's about two different visions for the future of Zimbabwe," Miliband said.

 

On Wednesday, police detained Tsvangirai for nearly nine hours before releasing him without charge.

A spokesman at the US embassy in Harare said that five Americans, four Britons and a number of local staff had been detained in Thursday's incident.

 

McGee said any dispute with the diplomats should have been taken up with the foreign ministry but Zimbawe was now "lawless".

 

"This government has been involved in a campaign of intimidation against its own citizens and now they are trying to intimidate diplomats, British and American diplomats, to keep us from going out in the countryside to witness what they are doing against the people of Zimbabwe."

 

Mugabe on Tuesday accused the West of using non-governmental bodies and opposition political parties to try and bring him down.

 

A source with Zimbabwe's National Association of Non-Governmental Organisations told AFP a letter from the Public Service Minister Nicholas Goche said all aid work was being suspended "until further notice".

 

"It has hereby come to my attention that a number of NGOs involved in humanitarian operations are breaching the terms and conditions of their registration", Goche said in the letter, according to the source, whose group received it Thursday.

 

Many Zimbabweans, particularly in rural areas, rely on food aid due to shortages of basic commodities such as cooking oil and cornmeal.

 

Violence has also mounted ahead of the vote.

 

According to the MDC, around 60 of its supporters have been killed by pro-Mugabe militias in the build-up to the run-off.

 

The opposition says the violence is intended to frighten off voters after Tsvangirai beat Mugabe in the first round of voting on March 29 but officially fell short of an outright majority.

 

Mugabe has ruled Zimbabwe uninterrupted since independence from Britain in 1980. Once seen as a post-colonial model, the economy is now in meltdown with the official inflation rate the highest in the world at 165,000 percent.