For those approaching the border crossing from the Lithuanian side, the Russian guards and military personnel are obscured by a bend in the road and the trees of the Ramoniškiai forest. Only a towering communication pole, watching and listening, shows how close they are.

Barely 50 vehicles a day pass through here making their way between Lithuania, once part of the Soviet Union, and Kaliningrad Oblast, a Russian exclave on the Baltic Sea. Wedged between Lithuania to its north and east, and Poland to its south, Kaliningrad is about 800 miles (1,300km) from Moscow.

This doesn’t look or feel much like a modern-day version of Berlin’s Checkpoint Charlie. Yet the 45km of land border on which the Ramoniškiai crossing sits – between the watery demarcation provided by the rivers Lepona to the south and Neman to the north – has become a worry for the government in Vilnius, the Lithuanian capital, a swift tank ride away.

In a few weeks Russia will roll out its massive Zapad (west) military exercise, bringing an estimated 100,000 troops and hardware to the European Union and Nato’s eastern borders. It follows constant cyber-attacks on Lithuanian government departments, described by officials as a “massive information war”, and the deployment last year of nuclear-capable Iskander missiles to Russia’s Baltic fleet base in Kaliningrad. On 1 August Nato fighters identified 18 Russian military jets in international airspace above the Baltic Sea. Most had been flying to and from the airbase in Kaliningrad without flight plans and with their transponders off, according to the Lithuanian ministry of defence.

Such is the anxiety, that when Russian military personnel take the military train from Kaliningrad to Moscow, a Lithuanian air force helicopter hovers overhead to ensure that no one illegally hops off en route. Earlier this year NATO deployed four battalion-sized battle-groups to Poland, Estonia, Latvia and Lithuania.Those with the darkest imaginations suggest Russia could one day choose to close the so-called Suwałki Gap, a 60-mile-long stretch of the Polish-Lithuanian border stretching from Kaliningrad to Russia’s close ally, Belarus, and cut off the Baltic states from the rest of Europe.

Facebook Twitter Pinterest Lithuanian and Russian border signs are seen near Sudargas border crossing point with Russia in Ramoniškiai. Photograph: Ints Kalniņš/Reuters

These are anxious times, thus Lithuania is building a €3.6m (£3.2m), two-metre-high border fence either side of the Ramoniškiai checkpoint,standing opposite the barbed wire erected by the Russians five years earlier.

Opposition politicians have condemned it as a feeble waste of money. “It’s stupid,” said Eugenijus Gentvilas, the leader of Liberal Movement in the Lithuanian parliament. “What can we avoid? Tanks? Of course not.” It is a view shared by locals who hold no great hope of resistance at the border. “If it happens, it happens,” said Jolanya Disjaitiene, 31, from the nearest village, Surdago, as she pushed her sleeping baby, Domas, home in his pram.

But just as Checkpoint Charlie was not really, at heart, about creating a physical barrier to invasion, but rather demarcation, control and red lines, so it is true of the Ramoniškiai fence.

Eimutis Misiūnas, Lithuania’s minister of the interior, told the Guardian the fence was primarily to deal with alcohol and tobacco smuggling and prevent illegal border crossings, but conceded that was not all.

“I have a second reason, everybody knows,” he said. “Estonia accused Russia of abducting an intelligence officer and we in Lithuania don’t want this to happen with Lithuanian officers. It is like a red line for Russia.”

The incident to which Misiūnas refers occurred three years ago, and has left a chill in the bones of politicians in the Baltic states ever since. On a Friday morning in September 2014, smoke grenades were detonated at an Estonian customs post, all radio and telephone signals were jammed, and armed Russian men dragged away a local official. His name was Eston Kohver. He was paraded on Russian TV and a year later sentenced by the Russian courts to 15 years in prison for espionage and other charges, including smuggling arms.

Estonia insisted the officer was abducted on Estonian soil. Russia’s domestic security service, the FSB, continues to claim, successfully in the Russian courts, that Kohver was on a “spying operation” on Russian territory, and deserves his punishment.

There are suspicions that the move was really about punishing the Estonian government. The incident had occurred two days after Barack Obama visited the capital, Tallinn, and vowed that an attack on Estonia would be regarded as being against all of Nato. He also hinted at a US naval base being established in the country.

Facebook Twitter Pinterest The Lithuanian interior minister, Eimutis Misiūnas, and officials inspect Sudargas border crossing point with Kaliningrad in Ramoniškiai. Photograph: Ints Kalniņš/Reuters

The abduction confirmed to many in Lithuania just how easily the Russians could do what they wished and avoid any repercussions, and that they were able to play fast and loose with the truth. Vilnius does not want to give them any chance to play the same tricks on Lithuanian soil.

In the fashion that Kremlin watchers have become familiar, Russia has responded to the building of the fence with a mixture of mockery and indignation. “In Kaliningrad area they have a brick factory and they suggested that to us we might need bricks for our fence [from that factory],” Misiūnas deadpanned.

“But we apologise. In this fence we don’t use any bricks … Usually we are building bridges between countries, but on this occasion we are building fences.”

He smiled. “We don’t fight with Russia, we don’t want to fight with Russia. We have this neighbour, we know how to live with this neighbour, and we live.”