New York [US], June 22 (ANI): UN Secretary-General Antonio Guterres on Tuesday expressed grave concern about the current tension between Lithuania and Russia over Kaliningrad.

"We are, obviously, following these developments very closely in and around Kaliningrad, including the warnings we have seen of possible escalation, which are very concerning," said UN spokesperson Stephane Dujarric.

"It's very important for us that all sides deal with their concerns through effective dialogue with appropriate diplomatic channels, in accordance with international law, and to refrain from any statement or from any action that could aggravate the tense situation," said the spokesperson.

Lithuania announced last week that it would ban the rail transit of goods subject to EU sanctions through its territory to the Russian enclave of Kaliningrad.

The Russian Foreign Ministry on Monday summoned the Lithuanian charge d'affaires and demanded the restrictions be immediately lifted, calling them "provocative" and "openly hostile."Later on Tuesday, the Russian Foreign Ministry summoned the head of the European Union Delegation to Russia and demanded the restrictions be lifted immediately, saying retaliation would follow if cargo transit was not restored.

Defence experts say Kaliningrad is the only Russian port on the Baltic Sea that is ice-free year-round and is an important launch point for the nation's naval fleet.

The key port's strategic location prevents ships from having to circumnavigate Scandinavia by way of a northern passage, traveling through the Arctic Ocean. According to Defence News, this is the route ships have to take from the second port of the Baltic Fleet in St. Petersburg.

Last Friday, state-owned Lithuanian Railways stopped the transit of goods between Russia and its Baltic Sea territory, the Kaliningrad region, citing EU restrictions. According to the Russian diplomat, Lithuania's ban on transit will ban the Baltic country itself and its citizens.

"We went to the Lithuanian Foreign Ministry today, we asked them a lot of questions. We talked about railway conventions, we said that you can't do this in a day, that you need to warn [us in advance]. It was simply read to us from a piece of paper that Lithuania, they say, has nothing to do with it, this is all the European Union, and what we are doing, we are simply doing what the European Union tells us," Ryabokon told the Rossiya 24 broadcaster. (ANI)