Gunmen prevented a group of 40 European observers on a fact-finding mission from entering Crimea on Thursday.
They were travelling by road from Odessa, a port on Ukraine’s Black Sea coast, towards Crimea, when they were detained by unidentified men in army uniform.
The group of observers from 21 Organisation for Security and Co-operation in Europe (OSCE) countries is supposed to be in Ukraine from March 5 to March 12.
Earlier the Crimean parliament said a decree making the region part of Russia was already in force and that any Ukrainian troops were now occupiers and must surrender or leave.
Uniformed men, believed to be Russian troops, although this is denied by Moscow, have been surrounding Ukrainian military bases for almost a week.
While many demonstrations in Ukraine’s Crimea support Russia’s intervention, there are also those who want Crimea to stay as part of Ukraine.
One pro-Ukraine student who tried to speak to reporters was accused by pro-Russians nearby of having come from Kyiv pretending to be Crimean
The student said: “I want Crimea to be with Ukraine. I don’t want to join criminal Russia. People, watch television, tell everyone about the real situation here.”
She is interrupted by another woman saying: “Go to Maidan and express yourself there.”
“I was born and have been living in Simferopol,” she replies.
She is then grabbed by a man wearing uniform, and she calls out: “Please film this.”