UN special envoy Robert Serry is seen during a meeting with Ukraine's acting President Oleksander Turchinov in Kiev on March 4, 2014.
The United Nations protested on Wednesday that its envoy to the tense Ukrainian region of Crimea had been threatened by unidentified armed men, but denied reports he had been kidnapped.
UN Deputy Secretary-General Jan Eliasson told reporters Robert Serry had been accosted by gunmen outside naval headquarters in Simferopol and warned "he should leave Crimea."
Serry had been travelling with a UN colleague.
When he was prevented from returning to his vehicle, he dropped into a cafe to use a telephone to alert the mission of the incident before heading back towards his hotel on foot.
Eliasson said it was not clear whether the envoy would have to halt his mission to Crimea.
But a journalist from British news network ITN who witnessed the incident reported on Twitter that Serry was headed for the airport.
Eliasson was speaking by video link from Kiev, where the United Nations is taking part in international efforts to mediate a stand-off between Russia and Ukraine's fledgling government.
Russian-backed forces seized control of Crimea and surrounded remaining Ukrainian bases there after a street revolt in Kiev ousted Ukraine's former pro-Moscow leader Viktor Yanukovych.