(ANSA) - ROME, MAR 31 - Foreign Minister Luigi Di Maio said Wednesday that Italy has expelled two Russians after an Italian Navy officer was caught while allegedly handing over classified documents to a Russian military official.
    The foreign ministry summoned the Russian ambassador to Rome in relation to the case earlier on Wednesday.
    "When the Russian ambassador to Italy was summoned to the foreign ministry, we expressed the Italian government's resolute protest and gave notice of the immediate expulsion of the two Russian officials involved in this extremely serious affair," Di Maio said via Facebook.
    "I thank the intelligence service and all the State bodies that work for the security of our country every day".
    Speaking subsequently in the Senate, Di Maio described the affair as "a hostile act of extreme gravity" for which "we immediately took the necessary measures".
    The Russian embassy said Ambassador Sergey Razov expressed his "sadness" about the decision and "the hope that what happened does not affect Italian-Russian relations".
    The Russian foreign ministry told ANSA that it was "saddened" by the expulsions.
    "We are examining the circumstances of this decision," the ministry said.
    "We will make an announcement about our possible steps in relation to this measure, which does not correspond to the level of bilateral relations".
    However, Interfax quoted Alexiei Cepa, the vice president of the Duma's international affairs committee, as saying Russia's response to the expulsions would be "symmetrical". The serviceman, a frigate captain, and a Russian official accredited to the Russian embassy were detained by the Carabinieri police's ROS unit late on Tuesday, sources said The Navy officer is accused of serious crimes regarding espionage and State security.
    In addition to the criminal investigation, military prosecutors have also opened a probe into the case.
    NATO documents regarding telecommunications were allegedly among the files the Navy officer handed over, in exchange for 5,000 euros in cash, the sources said.
    Britain was quick to express support for Italy.
    "The UK stands in solidarity with Italy and its actions today, exposing and taking action against Russia's malign and destabilising activity that is designed to undermine our @NATO ally," Foreign Secretary Dominic Raab said via Twitter.
    ANSA sources named the arrested man as Walter Biot, 56, an official working at the military policy office of the defence ministry's Joint Chiefs of Staff.
    Biot lives near Rome with his wife and four children. (ANSA).