ROME: Italy expelled two Russian officials on Wednesday after an Italian navy captain was caught red-handed by police selling secret documents to the Russians.

The Italian frigate captain was arrested on spying charges after officers tailing him saw him late Tuesday in Rome in a “clandestine meeting” with a Russian military officer, according to a police statement.

The two men met in a car park, according to media reports. Special operations police stopped them both but arrested only the navy officer, accusing him of passing on “confidential documents” in exchange for money.

The Russian, an embassy official, avoided custody thanks to diplomatic immunity, police said.

Italian Foreign Minister Luigi Di Maio summoned Russian ambassador Sergey Razov on Wednesday morning to lodge a formal protest.

The diplomat was notified of “the immediate expulsion of the two Russian officials involved in this very serious affair”, Di Maio said.

Eleonora Tafuro, a Russia expert at the ISPI think tank in Milan, said such incidents in Italy were rare.

“It is very serious ... and really takes us back to the Cold War period,” she told AFP. The ANSA news agency, quoting investigative sources, named the navy officer as Walter Biot, and said he worked in the military policy unit within the office of the Chief of the Defence Staff. That unit handled “all confidential and classified documents,” including NATO dossiers, the Corriere della Sera newspaper said.

It also reported that Biot received 5,000 euros ($5,860) in cash from his Russian contact. A NATO official referred queries to Italian authorities, saying: “We don’t comment on intelligence issues.”

The navy captain took pictures of secret documents on his computer screen and passed the files onto a pen drive which police confiscated, according to the AGI news agency. In London, Britain’s Foreign Secretary Dominic Raab expressed “solidarity” with Italy and condemned “Russia’s malign and destabilising activity that is designed to undermine our NATO ally”.