But Kieran Green of Care Canada, one of the groups ordered to halt operations in Zimbabwe, rejected those charges.
He said the NGO, which directly helps about half a million people though food aid, health and other development projects in Zimbabwe, had a strict policy of not politicising aid and had "built a reputation on it for many many years".
Green said Care had asked for evidence of the government's charges but had not received anything yet.
The UK and US later said that their diplomats had been freed.
The US government took complaints about the incident to the UN Security Council.
Condoleezza Rice, the US secretary of state, expressed anger over the incident and called on the council to act.
"This is really an outrageous act and we will have to look at what more we can do.
"But we are first going to raise it 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," she said.
|The US says police stopped their diplomats at a|
roadblock and slashed their tyres [File: EPA]
David Miliband, the British foreign secretary, called the detention of the diplomats a "serious incident" and said it underlined the hardship of life under Mugabe's government, which he said is "marked by brutal intimidation, by torture ... and by death".
The British and American governments demanded an explanation from the Zimbabwe government, with London summoning the country's ambassador to explain the events.
Haru Mutasa, Al Jazeera's correspondent in Harare, said that Zimbabwean opposition supporters have said that this could have been an intimidation tactic as the diplomats were in the rural area checking on those affected by recent political violence.
James McGee, the US ambassador to Zimbabwe, said: "The police put up a roadblock, stopped the vehicles, slashed the tyres, reached in and grabbed the telephones from my personnel.
|Harare said that the diplomats were at an|
opposition member's house [File: AFP]
"And the war veterans threatened to burn the vehicles with my people inside unless they got out of the vehicles and accompanied the police to a station nearby."
A US press spokesperson at the embassy told Al Jazeera that the group was "carrying out normal diplomatic business, collecting evidence from victims of political violence, when they were stopped in Bindura, by the Zimbabwean police.
"The police officials tried to take the diplomats to jail - in contradiction of the Vienna convention on diplomatic immunity.
"The US diplomats rang the US embassy who told the officials to go back to Harare.
"One car made it back. As one of the others drove off they were chased by police who tried to drive them off the road. The car was eventually brought to a halt at a road block – and its tyres were slashed.
"They were then surrounded by military, war veterans and police.
"Another car with security people which headed their way was also stopped and a satellite phone was stolen."
'Tried to flee'
The government in Harare said that the diplomats had been addressing a gathering at the home of an opposition party activist.
Matonga, the deputy information minister, said 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. 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."
|"We don't understand why they don't want to respect our laws"|
Bright Matonga, Zimbabwe deputy information minister
Speaking later to Al Jazeera, Matonga said that the envoys had been "distributing opposition campaign material" and were "operating outside their diplomatic mandate".
Matonga said that the envoys were required to inform Zimbabwe's ministry of foreign affairs if they intended to travel over 40km outside the capital and that the envoys had failed to do so.
"We don't understand why they don't want to respect our laws," he said.
The US state department said that the diplomats did inform Harare of their movements but Matonga said that while the US ambassador had submitted the necessary documents, Britain had not.
Diplomats are generally required to gain permission from the Zimbabwean government to move around the country.
Wayne Bvudzijena, a police spokesman, denied security agents had threatened the diplomats.
He said police at the scene intervened to rescue the diplomats from a threatening mob.
"It's unfortunate when diplomats behave like criminals and distort information," Bvudzijena said. "It is a very sad situation."