Lithuania has blocked Moscow from shipping some goods by rail through its territory to Russia's Baltic Sea exclave of Kaliningrad. Russia has fiercely condemned the move.
Reuters news agency reports that the move is part of European Union sanctions against Russia. The Baltic state of Lithuania is both a member of the EU and NATO.
The Russian exclave is surrounded by Lithuania and Poland.
Kaliningrad governor Anton Alikhanov estimated that up to 50 percent of all kinds of goods may be affected by the ban, including coal, metals and construction materials.
Russian presidential spokesperson Dmitry Peskov told reporters on Monday that the decision is unprecedented and unlawful. The Russian foreign ministry summoned Lithuania's chief diplomatic representative in Moscow to lodge a protest and threaten a possible countermeasure.
Meanwhile, the Associated Press and others reported that the Lithuanian government defended the measure, noting that the ban is in line with EU sanctions.
The EU's top diplomat, Josep Borrell, also said on Monday that land transit had not been stopped or banned and the transport of passengers and goods not subject to sanctions is continuing.