Ivan Simonovic, the global organisation's assistant secretary-general for human rights, travelled to Ukraine last week, making a stop in Kiev, before traveling on to Kharkiv, where he is at present.
UN spokesman Stephane Dujarric said, however, that travel to the Black Sea peninsula currently under the control of Russia-backed authorities has been taken off Simonovic's agenda for the time being
Pro-Kremlin militants today ordered a suspension of all flights in or out of Crimea's main airport in Simferopol except those connecting to Moscow.
"Currently the logistics do not allow us to fly to Crimea and we are looking at the overall security issue," the spokesman said, adding that officials "are taking things one day at a time."
Dujarric said that in Kharkiv, Simonovic "met local authorities to discuss human rights-related measures that could help de-escalate tensions," and plans to travel on Wednesday to the city of Lviv in western Ukraine.
Pro-Moscow authorities who have seized control in Crimea and are seeking to join with Russia, have taken a number of steps in recent days to isolate the region from the rest of Ukraine and control entry points.