Russia has accused Lithuania of "openly hostile" restrictions on rail freight traffic to the Russian exclave of Kaliningrad in the wake of EU sanctions, fueling tensions with the Baltic states.

If cargo transit between Kaliningrad and the rest of Russia via Lithuanian territory is not quickly and fully restored, Russia "reserves the right to take action to protect its national interests," the Foreign Ministry in Moscow threatened on Monday.

Brussels stressed that the measures were in line with EU sanctions, but announced a review of the guidelines on sanctions.

According to the Russian Foreign Ministry, the Lithuanian chargé d'affaires was summoned to Moscow to protest against the "provocative" measures.

From the Russian point of view, the restriction on the delivery of goods violates an agreement between Russia and the EU from 2002. However, Lithuanian Foreign Minister Gabrielius Landsbergis and EU foreign policy chief Josep Borrell said the measures were in line with those imposed by the EU because of the Russian Sanctions imposed for aggressive war against Ukraine.

Kaliningrad, formerly East Prussian Königsberg, lies on the Baltic Sea between Lithuania and Poland and has no direct land connection to Russia.

The territory is of great strategic and military importance for Russia.

The port city is home to the Russian Baltic Fleet.

According to Russia, it has stationed nuclear-capable Iskander missiles in the exclave.

Kremlin: Unprecedented decision

Landsbergis said during deliberations of EU foreign ministers in Luxembourg that the transport restrictions affect steel products and other goods made from iron ore.

According to the governor of Kaliningrad, Anton Alikhanov, 40 to 50 percent of imports could be affected by the "blockade" - in addition to metal, coal, building materials and technological goods.

The Kremlin spoke of an "unprecedented" decision by Lithuania that violated all principles.

Kremlin spokesman Dmitry Peskov said: "The situation is more than serious." It will now be examined with a view to "reactions".

He did not specify the nature of these countermeasures.

Landsbergis said of the freight restrictions: "It's not Lithuania that is doing something - it's the European sanctions that came into force on June 17." The restrictions are "in consultation with the European Commission and in accordance with the directives of the European Commission “ has been implemented.

The affected customers have also been informed.

EU: Land route is not blocked

For his part, Borrell emphasized that it was not a question of a "blockade" of Kaliningrad, but merely a ban on the transport of certain types of goods.

"Overland transit between Russia has not been stopped or banned," the EU foreign policy chief said at a press conference in Luxembourg.

However, the EU will review the guidelines on sanctions again, Borrell promised.

Ukraine, meanwhile, underlined its solidarity with Lithuania.

"Russia has no right to threaten Lithuania," Foreign Minister Dmytro Kuleba said on Twitter.

"We welcome Lithuania's principled position and firmly support our Lithuanian friends."

The relations between Russia and Lithuania as well as the two other Baltic countries Latvia and Estonia are extremely tense due to the Ukraine war.

The Baltic states fear becoming the next target of Russian military aggression.

The three countries belong to both the EU and NATO.