Lithuania on Monday alleged that one-third of Russian diplomats in the EU and NATO Baltic state were working for spy agencies, and warned that Moscow could test the alliance with unconventional tactics.

Lithuania's intelligence agency said it kicked out three Russian spies last year, adding that Moscow was increasingly interested in the NATO member's military infrastructure.

"One-third of Russian diplomats working in Lithuania are intelligence agency officials or are linked with intelligence agencies," the State Security Department said in its annual report.

Among those expelled was former consul in the Lithuanian port of Klaipeda Vladimir Malygin, whom Vilnius identified as a Russia Foreign Intelligence Service (SVR) official.

The report said Malygin was seeking information about Lithuania's first floating LNG terminal which opened in January, breaking Russian giant Gazprom's monopoly on gas supplies in the Baltic states.

"We are a NATO frontier country hugely affected by unfriendly propaganda, incitement of ethnic minorities directed against our state and its interests," President Dalia Grybauskaite said Monday responding to the findings.

In a separate report also released Monday, Lithuania's military intelligence pointed to the danger of Russia launching a so-called "hybrid war" on Baltic NATO members by using "unconventional or covert military measures" to test the alliance's commitment to collective defense.

"We cannot rule out that Russia may resort to such measures against one of the alliance's members hoping that NATO would not be able to respond in due time and manner," reads the document.

Having all joined the EU and NATO in 2004, Lithuania and fellow Baltic states Latvia and Estonia are concerned about Russia's actions in Ukraine and fear that Moscow could attempt to destabilise its Soviet-era Baltic backyard. (+++++)