Vice News said in a statement Thursday that its correspondent was released after being detained in Eastern Ukraine.
The media outlet said the U.S. journalist, Simon Ostrovsky, was safely released and is in good health after being detained in Slovyansk, Ukraine, by pro-Russian forces.
"I'm out and safe. Thank you all for your support. Had no idea I had so many good friends," Ostrovsky said in a tweet.
Vice News also released a short video report that featured Ostrovsky before his capture reporting on a shooting that occurred at a checkpoint over the weekend. The video includes footage from a news conference with what the media outlet describes as the reporter's "future captor."
Pro-Russian separatists had told The Associated Press on Wednesday he was being detained for suspicion of spying for an ultra-nationalist group.
The news outlet did not provide further detail, but the State Department had condemned the kidnapping Wednesday and called on Russia to use its influence in the region to help secure his release.
State Department spokeswoman Jen Psaki on Thursday said she had seen the reports that he had been freed.
"We welcome the news, of course, and would be greatly relieved by such a development," she said.
The State Department said the kidnapping and other "recent hostage takings" directly violated an agreement to de-escalate the situation there by the United States, Russia, Ukraine and the European Union.
The agreement for separatists to cease their occupation of government buildings in exchange for amnesty has been partly ignored, causing U.S. officials to say Russia has not held up its end of the deal.
— Rebecca Shabad contributed