Austria has expelled three Russian diplomats, accusing them of spying.
The diplomats, who have already left the country, used a "forest of antennas" installed on the roofs of diplomatic buildings to gather information, Foreign Minister Beate Meinl-Reisinger said.
A report by the Austrian Broadcasting Corporation (ORF), confirmed by the foreign ministry, said the antennas were on the roof of the Russian embassy in Vienna and at a Russian diplomatic compound.
"We regard this latest unfriendly move by the Austrian authorities as entirely unjustified, purely politically motivated and categorically unacceptable," the Russian embassy said in a statement.
"Moscow will undoubtedly respond harshly to these completely ill-considered actions on the part of the Austrian side."
