Manfred Nowak: "It is totally unacceptable treatment"
The UN torture investigator has been denied entry to Zimbabwe, despite being invited by the country's Prime Minister Morgan Tsvangirai, the UN says.
Manfred Nowak said he was stopped by immigration officials after landing at Harare airport on Wednesday evening.
Mr Nowak's week-long fact-finding mission was blocked by Zimbabwe's foreign ministry at the last minute.
Early on Thursday, Mr Nowak left the country on a flight to Johannesburg, a UN spokesman said.
The blocking of Mr Nowak's visit comes amid a renewed political crisis between power-sharing rivals Mr Tsvangirai and President Robert Mugabe.
Supporters of Mr Mugabe's Zanu-PF party have reportedly launched a campaign of violence on Mr Tsvangirai's MDC (Movement for Democratic Change) party.
Mr Tsvangirai stopped co-operating with the unity government two weeks ago.
He was angry at perceived failure by Zanu-PF to implement measures agreed to as a part of the power-sharing deal and the jailing of a senior MDC member on terrorism charges that he says are trumped up.
Battle of wills
The BBC's Karen Allen, in neighbouring South Africa, says the decision to cancel the trip is bound to be seen by some as a battle of wills between the two major parties.
And ahead of a regional meeting on the crisis, human rights group Amnesty International has warned the country is on the brink of sliding back into last year's post-election violence.
Mr Nowak earlier said he had received "two completely different messages" from the Zimbabwean government - but added that he would try to meet Mr Tsvangirai on Thursday.
Recent allegations that MDC supporters and human rights defenders have been arrested, harassed and intimidated... highlight the urgency of objective fact-finding
"I got the clear message from the prime minister that it is his understanding that the mission is going on," he said.
"That leads me to the conclusion that there must be some kind of misunderstanding between the different cabinet members."
The UN says Mr Nowak - the special rapporteur on torture - was informed of the cancellation only when he was in South Africa on his way to Zimbabwe.
He had been initially invited by Justice Minister Patrick Chinamasa - a Zanu-PF member - to meet officials and rights activists, inspect prisons and police stations and compile a report for the Security Council.
But the UN said Harare had called off the visit because of an unanticipated meeting with the southern African regional group, Sadc.
A Sadc team is due in Harare on Thursday to try to resolve the political crisis.
Nevertheless, Mr Nowak said he would travel to Zimbabwe, following an invitation from Mr Tsvangarai.
The UN said in a statement that Mr Nowak welcomed "all efforts to resolve the political crisis", but that the Sadc meeting was not a valid reason to cancel his visit.
"Recent allegations that MDC supporters and human rights defenders have been arrested, harassed and intimidated during the past few days highlight the urgency of objective fact-finding by an independent UN expert," the UN said.
On Tuesday, Mr Tsvangirai's MDC party said there had been an increase in violent attacks on its members.
Party spokesman Nelson Chamisa said a senior official had been stopped and beaten by Zanu-PF supporters on Tuesday morning. Days earlier, an MDC residence was raided by police.
Zanu-PF has described the comments as "cheap propaganda".
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