Meet Kaliningrad, the "amber city" of Russia 2:02
(CNN) --
Tensions are rising around the Russian enclave of Kaliningrad, an isolated but strategically important territory on the Baltic coast that could soon be drawn into the Kremlin war.
Russia has reacted furiously after Lithuania banned the passage of sanctioned goods through its territory and into Kaliningrad.
But Lithuania says it is merely maintaining European Union sanctions, and the European bloc has given its support.
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The dispute now threatens to aggravate tensions between Moscow and the European Union, which has presented several packages of sanctions on Russian products.
Here is what you need to know about Kaliningrad, its history and its importance to Russia.
Residents of Kaliningrad have been urged not to panic after this week's rise in tensions.
What caused this dispute?
Since Russia invaded Ukraine in late February, experts have feared that Kaliningrad could become a flashpoint for tensions between Moscow and Europe.
It is the westernmost territory of Russia and the only part of the country surrounded by states of the European Union;
Lithuania lies between it and Russia's allied nation Belarus, while Poland borders it to the south.
Location of the Russian territory of Kaliningrad.
On Monday, Kremlin spokesman Dmitry Peskov said the move was unprecedented and considered illegal by Russia.
"It's part of a lockdown, of course," he said.
Other Russian officials have threatened a response.
Nikolai Patrushev, secretary of the Security Council of the Russian Federation, said: "Russia will certainly respond to these hostile actions."
Measures are being developed in an interdepartmental format and will be adopted in the near future.
Its consequences will have a serious negative impact on the Lithuanian population," according to the Russian state news agency RIA Novosti.
Among the sanctioned products that the European Union has banned from exporting to Russian territory are construction machinery, power tools and other industrial equipment, according to the Russian state news agency TASS, citing the Ministry of Economic Development.
Some luxury products are also included.
Lithuania has not imposed "unilateral, individual or additional" restrictions, its foreign ministry said in a statement on Monday.
The Lithuanian Chargé d'Affaires in Moscow was summoned to the Russian Foreign Ministry on Monday and told that if the transit of goods to the Kaliningrad region is not fully restored, Russia reserves the right to take measures to protect their national interests.
But the European Union, whose sanctions Lithuania applies by blocking transit, has backed its member state.
Photographs from Russia's war in Ukraine displayed along the railway station where trains from Moscow to Kaliningrad pass, as part of a protest by Lithuanians against the invasion.
Speaking to Reuters, Dmitry Lyskov, a representative of the regional government, was forced to urge residents not to panic buy in response to the controversy.
Sanctioned products will now have to travel by sea.
A Lithuanian official, Rolandas Kacinskas, stated on Tuesday that "the transit of passengers and goods not sanctioned by the European Union to the Kaliningrad region through the territory of Lithuania continues without interruption. [Lithuania] has not imposed any unilateral restrictions, individual or additional to the transit and is acting fully in accordance with the legislation of the European Union".
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What is Kaliningrad?
Kaliningrad is a Russian exclave located between Poland and Lithuania.
It was captured by Soviet troops from Nazi Germany in April 1945 and later became part of Soviet territory as a result of the Potsdam Agreement.
In 1946 it was renamed from the German Königsberg.
For decades, it was a heavily militarized region, closed to foreigners.
But in recent years Kaliningrad has become an emerging tourist destination, hosting matches during the 2018 World Cup in Russia.
It has a population of around one million inhabitants, most of whom live in or near the capital of the same name.
The exclave is one of the most prosperous regions of Russia, with extensive industry.
Its port, Baltiysk, is the westernmost in Russian territory and, significantly, it is ice-free throughout the year.
The streets of the main city are lined with grand examples of old German architecture alongside dingy concrete Soviet apartment blocks.
Kaliningrad in the build-up to the 2018 World Cup, which put the region on its biggest international cultural platform to date.
But the importance of Kaliningrad is due above all to its location on the map.
A thin strip of land south of Kaliningrad separates it from Belarus and connects Polish and Lithuanian territory.
Known as the Suwalki gap or corridor, it is the only land link between the Baltic countries and the rest of the European Union.
Kaliningrad is also the headquarters of the Russian Baltic Fleet.
RIA Novosti reported on Monday that the fleet had started previously planned rocket and artillery exercises, saying "about 1,000 servicemen and more than 100 units of military and special artillery and missile equipment are taking part in the exercises."
In 2002, the European Union and Moscow reached an agreement on travel between Russia and Kaliningrad, before Poland and Lithuania joined the European Union in 2004. With the accession of these countries, the exclave was surrounded on three sides by territory. from the EU.
Russia claims that the 2002 agreement has been violated.
Nuclear presence?
Kaliningrad's importance has increased for Russia now that Sweden and Finland are expected to join NATO.
Dmitry Medvedev, deputy chairman of Russia's National Security Council, said in May that the accession plans meant that "it will no longer be possible to talk about a non-nuclear status of the Baltic: the balance must be restored."
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Russia has long shown its rejection of the presence of NATO countries around Kaliningrad.
"They moved NATO infrastructure alongside our borders," Russian Foreign Minister Sergey Lavrov told CNN in 2015, after reports that Russia had moved nuclear-capable Iskander missiles into the region.
"And this is not United States territory."
Russia has not acknowledged that it has nuclear weapons in Kaliningrad, but in 2018 the Federation of American Scientists concluded that Russia had significantly modernized a nuclear weapons storage bunker in the region, based on analysis of satellite imagery.
Since the Russian invasion of Ukraine, Lithuania has urged NATO to increase the deployment of troops on its territory.
In April, President Gitanas Nauseda said NATO's Enhanced Forward Presence Battalion should be "at least" brigade-sized, and called for the Suwalki corridor to be reinforced.
Conflict Russia - UkraineLithuania
