The United Nations says its human rights expert, Manfred Nowak, has been deported from Zimbabwe after being detained by security officials on arrival.
Mr Nowak had been trying to enter the country for a week-long fact-finding mission.
He says officials refused to allow him in, despite having a written invitation from Zimbabwe's Prime Minister, Morgan Tsvangirai.
It comes amid rising tension between the two major political parties following the prime minister Morgan Tsvangirai's withdrawal of cooperation with Zimbabwe's unity government.
