Lithuanian Prime Minister Saulius Skvernelis on Thursday said the Baltic NATO member had broken up a local spy ring working for Russia that had posed a threat to national security.
He spoke after Lithuanian officials announced they had detained several Lithuanian citizens and one Russian on suspicion of espionage.
"Our security services took timely action against a Russian spy ring in Lithuania and prevented actions that threatened national security," Skvernelis told AFP.
"These were not solitary instances but methodic action directed against our state." The Russian foreign ministry dismissed the case as another instance of "a Russophobic policy".
On Wednesday Lithuanian prosecutors said several individuals, including former Lithuanian lawmaker Algirdas Paleckis, were arrested in an espionage probe earlier this year.
They declined to name the exact number or identity of the others but police chief Linas Pernavas specified they were all Lithuanian with the exception of one Russian.
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Prosecutor general Evaldas Pasilis said Russian intelligence services were notably interested in information regarding an ongoing criminal case concerning the 1991 crackdown on Lithuania's independence drive.
Earlier this year, Lithuanian prosecutors called for five Russians, including an ex-defence minister, and a Belarusian to be sentenced to jail in absentia over the January 1991 attack on a Vilnius television that left 14 civilians dead.
The verdict is expected in February. Moscow has called the trial "illegal" and rejected requests to extradite the suspects and question ex-Soviet leader Mikhail Gorbachev, who is 87.
The spy case is the latest in a string of espionage allegations in the Baltic states involving Russia's intelligence service.
The incidents come amid tensions sparked by Moscow's 2014 annexation of Crimea from Ukraine, a move that deeply rattled nearby NATO members.