A U.S. Embassy spokesman told a Russian news agency Thursday that Russia has expelled the deputy chief of of the U.S. mission in Moscow.

No details were given of why Bart Gorman was expelled. The State Department confirmed the expulsion, calling it unprovoked.

The move comes amid heightened tensions between Russia and the U.S., fueled by fears that Moscow plans to invade Ukraine.

Spokesman Jason Rebholz told the state RIA Novosti news agency that Gorman was second in command in the U.S. Embassy in Moscow and had an open visa. He spent less than three years in Moscow, the report said.