Pro-Russian separatists are holding an American journalist in the Ukrainian town of Slaviansk.
Simon Ostrovsky, who works for Vice News, is apparently being held in the local headquarters of the Ukrainian security services, which have been seized by pro-Russian forces.
A spokeswoman for the insurgents said Mr Ostrovsky is "fine" but is "suspected of bad activities" and is under investigation, according to the Associated Press.
Tensions remain high in eastern Ukraine after at least three died in a day of shooting during what was supposed to be an Easter truce.
In an exclusive interview with NBC News, the Ukrainian Prime Minister warns of the dangers of unchecked Russian expansion and aggression.
Russia, the US and the EU say that all sides have agreed to steps to "de-escalate" the crisis in Ukraine at talks in Geneva.