Zimbabwe's foreign minister is calling a visit by the U.N. torture investigator "a provocation of the highest order."

The foreign minister, a ranking member of President Robert Mugabe's party, on Friday sharply criticized Manfred Nowak for coming to Zimbabwe earlier this week after he was asked to delay the trip.

Simbarashe Mumbengegwi said what Nowak did was unprecedented in the history of U.N. protocol and that he had forced himself on a country.

Nowak had planned to investigate alleged attacks on Prime Minister Morgan Tsvangirai's supporters by militants linked to Mugabe's party.

Nowak spent the night in the Harare airport before being sent back to South Africa. On Thursday, he called his treatment a "serious diplomatic incident."