Romania's Intelligence Service said on Monday it had identified a sabotage network coordinated by Russia, which it believed was responsible for a fire in September at an industrial site in central Romania near a state-owned weapons company.
The European Union and NATO states share a land border of more than 600 km (370 miles) with Ukraine, and centrist president Nicusor Dan has said it is the target of a hybrid war waged by Russia to destabilize nations that support Kyiv.
The attacks range from drone incursions into Romanian airspace to cyberattacks, disinformation campaigns, acts of sabotage and attacks on cargo vessels near Romanian waters, Dan has said.
Russia's embassy in Bucharest could not immediately be reached for comment outside business hours, but Moscow has repeatedly denied such accusations.
Romanian organized crime prosecutors said they were seeking the extradition of two Belarusian suspects apprehended in Germany and one Ukrainian detained in Poland who were all suspected of involvement in the arson case.
The Intelligence Service said all three were part of the network coordinated by Russia, whose coordinators had assigned it targets including "state and private weapons production facilities, as well as other objectives of military and industrial interest."
NATO members Romania, Bulgaria, Poland targets of recent Russian attacks
A year ago, Poland and Romania detained eight people suspected of involvement in a Russian plan to send exploding parcels to Ukraine.
Dan accused Russia of escalating its attacks on NATO's eastern flank this month after a series of drone strikes on cargo vessels in the Black Sea.
At least eight cargo ships have been hit off the coast of NATO members Romania and Bulgaria in the past three weeks. Some 34 sailors are reported dead or missing.