An American journalist for Vice News is being held captive by pro-Russian gunmen following his reporting on the turmoil in Ukraine.

Simon Ostrovsky had covered the conflict over Crimea for weeks and went missing Tuesday. His disappearance is the latest example of a crackdown on journalists by Russia and its supporters, prompting a warning from the U.S. State Department.

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“We call on Russia to use its influence with these groups to secure the immediate and safe release of all hostages in eastern Ukraine,” said spokeswoman Jen Psaki, who noted that such actions are in violation of a commitment by Russia and Ukraine made last week in Geneva.

A spokeswoman for the pro-Russian insurgents told the Associated Press that Ostrovsky was “suspected of bad activities.” She added, “He’s with us. He’s fine.”

Last month, a Bulgarian journalist and other reporters were held at gunpoint in Crimea. That followed the closure of Black Sea TV, Crimea’s only independent channel. Other journalists have been confronted by armed men, beaten and detained.

This story was produced by The Foundry’s news team. Nothing here should be construed as necessarily reflecting the views of The Heritage Foundation.