MOSCOW, May 4 (Xinhua) -- Russia on Monday condemned Austria's expulsion of its diplomats as "unjustified" and "politically motivated," warning of possible retaliation.

Earlier in the day, Austria declared three Russian diplomats persona non grata and expelled them for suspected espionage.

In a statement posted on social media, the Russian Embassy in Vienna called the move "outrageous" and "absolutely thoughtless," saying the Austrian authorities failed to provide evidence of any violations by the diplomats.

"We consider this another unfriendly step by the Austrian authorities to be unjustified, exclusively politically motivated, and categorically unacceptable," said the statement.

Moscow also warned that a harsh reaction could follow and that Austria would bear responsibility for any further deterioration in bilateral relations.