The base, when completed, will even have its own swimming pool, skating rink and barber shop, according to public documents. This week workmen were erecting a fence in a cornfield outside the village of Soloti near a railway line that links Soloti with Moscow and Luhansk, the adjacent Ukrainian region that is controlled by pro-Moscow separatists to mark out the perimeter, Reuters reported.

In almost the same spot there was a flurry of military activity in April last year that coincided with intense fighting across the Ukrainian frontier that lies about 25 km (15 miles) away. A squadron of Mi-24 attack helicopters was seen there at the time, as well as army tents and trucks.

NATO has accused Russia of using makeshift bases for sending soldiers and hardware into Ukraine to support pro-Russian separatists fighting Kyiv.

While denying its military is in Ukraine, the defense ministry did not reply to written questions from Reuters about the purpose of the base it is building and whether there was any connection to the Ukraine conflict.

According to tender documents published on the Russian government website, the ministry is building the military base on a 300-hectare site near Valuyki, a small town not far from Soloti.

The ministry intends to build nine barracks for 3,500 soldiers, warehouses for rockets, artillery weapons, and other munitions with a total area of over 6,000 square meters.

The documents also stated there would be a large training complex, and an infirmary for 50 beds, which can be expanded in case of "massive influx of wounded".

They did not give the exact location of the base, but local residents in Soloti said they believed it would be on their doorstep. "They are building a military town," said Alexander Panchenko, a local resident whose house overlooks farmland where preparatory work is underway for a big construction project.

A man in Soloti, who called himself a representative of the Federal Agency for Special Construction - which overseas construction of defense installations - refused to talk about the work, saying only that "a secret facility" was being built.

The field where the work was underway is near a railway line that links Soloti with Moscow and Luhansk, the adjacent Ukrainian region that is controlled by pro-Moscow separatists.

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.

According to the procurement documents, the defense ministry plans to use the base to train soldiers on artillery and army air defense, as well as in driving tanks and armored personnel carriers.

The plan includes a site for studying the tactics of the U.S. Army, which was called a "likely enemy" in the document.

On top of that, the base will include a headquarters with a communications node and a residential complex of more than 1,000 apartments.

The document, seen by Reuters, requires the completion of the first stage - the base design and initial construction and installation works - by April 29, 2016.