According to the Austrians, a recently-retired colonel was spying for the Russians for decades, starting in the 1990s. The intelligence service of an unidentified ally apparently provided the tip-off.

“If the suspicion is confirmed, such cases… do not improve relations between Russia and the European Union,” said Austrian Chancellor Sebastian Kurz, according to Reuters.

The revelation is particularly damaging for Russia as Austria, with its conservative government, was relatively friendly toward the EU’s eastern neighbor. The country was one of the few EU member states that did not kick out Russian diplomats following the Novickok poisoning in the U.K. of former double agent Sergei Skripal and his daughter.

The Austrians say they want the Russian to provide “transparent information.” As for the Russians, Foreign Minister Sergei Lavrov said he was “unpleasantly surprised” by the news. He claimed Russia knew nothing about the colonel.

Apart from the Skripal poisoning incident—which claimed the life of a woman who came into contact with the poison—Russia-EU relations have also been cooled by the revelation of a string of cyber-attacks by Russian intelligence, targeting everyone from the Organisation for the Prohibition of Chemical Weapons to a meeting of the World Anti-Doping Agency. This drew an angry response from the U.S., which indicated it was willing to deploy its own cyber-attack capabilities on behalf of its NATO allies.