LONDON -- U.S.-Russian dual citizen Ksenia Karelina was released from Russian prison in an overnight prisoner exchange, Secretary of State Marco Rubio announced on Thursday.

Karelina -- a ballet dancer -- was serving a 12-year prison sentence in a penal colony. The exchange took place overnight in Abu Dhabi in the United Arab Emirates. Karelina's lawyer Mikhail Mushailov confirmed to ABC News that she had been released.

Secretary of State Marco Rubio confirmed the exchange in a tweet, writing, "American Ksenia Karelina is on a plane back home to the United States. She was wrongfully detained by Russia for over a year and President Trump secured her release."

This is a developing story. Please check back for updates.

ABC News' Joe Simonetti and Cindy Smith contributed to this report.