While there have been no clashes between the former Cold War rivals, Russia is building up forces on its western frontiers at a time when the NATO alliance is staging major military exercises and increasing deployments on its eastern flank, Reuters reports.
A Reuters reporter who visited the Russian town of Klintsy, about 50 km (30 miles) from Ukraine, saw a makeshift army camp, large numbers of newly-arrived servicemen and military vehicles.
Two soldiers in camouflage gear who were manning a checkpoint in a forest turned the reporter away, saying they were guarding a "special military site".
Last year, Reuters also reported on construction of two other bases further to the south on Russia's border with Ukraine.
The defense ministry has not acknowledged the deployment of troops to Klintsy, which usually serves as a stop for truck drivers traveling between Russia, Ukraine and Belarus.
However, a town council official said Klintsy had been chosen as the site of a newly-formed division, and that so far about 240 soldiers had arrived. "What's to hide? That they've come? They've arrived," said council deputy chairman Oleg Kletny. "They're going to be garrisoned here."
When completed, the base will be the latest component in a build-up of forces along a line running from the Baltic Sea in the north to the Black Sea in the south.
Russia has pulled out of the treaty on Conventional Forces in Europe, a post-Cold War pact that limits the deployment of troops in Europe, so it is free to move extra troops and hardware to its western border.
Read alsoUN has credible reports on troops, heavy arms arriving from Russia to DonbasOn Monday Klintsy, normally a sleepy town, was a hive of military activity. The Reuters reporter saw about a dozen tents and the same number of military vehicles in a temporary camp in a clearing in a forest where the troops will be billeted until their permanent base is ready.
Military trucks drove through the town, which lies in an area that is the closest point on Russian territory to the Ukrainian capital, Kyiv, just 280 km away.
About a dozen servicemen were at a gas station near the camp, buying food supplies. A road near the camp was blocked off by antitank obstacles and road spikes.
Last week, Russia's Interfax news agency quoted an unnamed source familiar with the deployment to Klintsy as saying it "can be seen as a response to the growing activity of the North Atlantic Alliance near Russia's borders".
The defense ministry did not reply to questions from Reuters about the base and its purpose.
Council deputy chairman Kletny said the troops, from a motorized infantry division, started arriving on May 30. They came from a base in Yekaterinburg, in the Ural mountains region about 2,000 km to the east of Klintsy.
He said they were deployed following a decision earlier this year by Defence Minister Sergei Shoigu to create three new divisions. The soldiers will be eventually garrisoned in the grounds of a disused military base in Klintsy which they are renovating, said Kletny.
"It's good that the military will come; our demographic situation will improve, we'll get a bigger population. If servicemen come her with their families, that will be good too," he told Reuters.
A notice lodged with Klintsy town council and seen by Reuters stated that approval is being sought for re-zoning and construction works on two plots of land with a total area of 142 hectares (351 acres), or about the size of 140 soccer pitches.
The plots of land would be used "for the interests of the Russian armed forces", according to the notice.