Pro-Russian separatists who claim to have seized unarmed OSCE observers in eastern Ukraine have released images of what appear to be the men's official identity cards.
The German-led group of mediators were travelling on a bus in Slaviansk, which has been under the control of militant separatists for two weeks, when they were said to have been detained at a checkpoint.
Vyacheslav Ponomaryov, the self-proclaimed mayor of the town, accused one of the members of the group of a being a spy for Kiev.
"People who come here as observers bringing with them a real spy: it's not appropriate," he told Reuters.
The observers are being held in a security service building, according to the Ukrainian government.
More top news
Tom Bradby will play host to the leaders of the three main parties, as well as the biggest names from the worlds of arts and culture.
One of the greatest sporting events on earth gets underway this week as the Ryder Cup heads to Scotland, here's everything you need to know
A toddler was in need of an unusual rescue after she got a kettle stuck on her head while playing at home in Chile.