DONETSK, Ukraine >> Pro-Russian gunmen in eastern Ukraine admitted on Wednesday that they are holding an American journalist who has not been seen since early Tuesday.

Simon Ostrovsky, a journalist for Vice News, has been covering the crisis in Ukraine for weeks and was reporting about groups of masked gunmen seizing government buildings in one eastern Ukrainian city after another.

Pro-Russia insurgents who have been occupying police stations and other public buildings in eastern Ukraine for more than a week are defying the accords that Russia and Ukraine signed last week, urging all parties in Ukraine to lay down the arms and vacate the public offices.

Members of the nationalist Right Sector movement have also been occupying two buildings in the capital, Kiev, for months, but authorities have said the priority is to get the gunmen in eastern Ukraine to vacate the buildings they hold.

Stella Khorosheva, a spokeswoman for the pro-Russian insurgents in the eastern city of Slovyansk, confirmed Wednesday that Ostrovsky was being held at the local branch of the Ukrainian security service that they seized more than a week ago.

“He’s with us. He’s fine,” Khorosheva told The Associated Press. When asked why Ostrovsky was held captive, Khorosheva said he is “suspected of bad activities,” which she refused to explain. She says the insurgents are holding Ostrovsky pending their own investigation.

In a statement, Vice News said it “is in contact with the U.S. State Department and other appropriate government authorities to secure the safety and security of our friend and colleague, Simon Ostrovsky.”

Ukraine has been engulfed in its biggest political crisis since the fall of the Soviet Union. Months-long anti-government protests in the capital of Kiev culminated in President Viktor Yanukovych fleeing to Russia in late February.

The acting government has accused Russia of orchestrating the unrest in eastern Ukraine which it fears Moscow could use as a pretext for an invasion. Last month, Russia annexed Crimea weeks after seizing control of the peninsula.

On Tuesday, Ukraine’s acting President Oleksandr Turchynov ordered security forces to resume operations in the country’s east after the bodies of two people allegedly abducted by pro-Russia insurgents were found. There were no reports of any such operations by midday Wednesday.