A Russian court has convicted of espionage an Estonian security officer who Tallinn and Brussels say was abducted in Estonia a year ago and dragged across the border into Russia, drawing sharp rebukes from Estonia and the European Union.

The court in Russia's northwest Pskov region, which borders Estonia, sentenced Eston Kohver on August 19 to 15 years in prison on charges of spying, smuggling, possession of weapons, and illegal crossing of the state border. He was also fined 100,000 rubles ($1,523).

The court ruled that Kohver must serve his sentence at a strict security penitentiary in Russia.

The U.S. State Department called on Russia to immediately release Kohver, saying his "abduction, detention, and now conviction on baseless charges demonstrate a flagrant disregard" by Russian officials toward the rule of law.

The European Union immediately protested the verdict and called on Moscow to release Kohver and guarantee his safe return to Estonia.

EU foreign policy chief Federica Mogherini said on August 19 that Kohver's "abduction and subsequent illegal detention in Russia constitute a clear violation of international law." She also said Kohver had been deprived of the right to a fair trial because it was held behind closed doors, the Estonian consul was not allowed to be present, and "Kohver was deprived of adequate legal aid."

Estonian Prime Minister Taavi Roivas also condemned the verdict, saying in a Twitter post that Kohver's "illegal detention constitutes a grave violation of international law."

Moscow claims that Kohver, an officer of Estonia's internal security service, was seized inside Russian territory on September 5 carrying cash, weapons, and recording devices while on an undercover operation.

But Tallinn says Russian agents seized Kohver at gunpoint on Estonian territory and that footprints and other markings on the ground proved he was ambushed and forcibly dragged across the border in a well-planned kidnapping operation that included the use of stun grenades.

A bilingual protocol apparently signed by both Russian and Estonian border officials who inspected the scene hours after the incident appeared to corroborate that view. It said the footprints indicated a group of individuals entered Estonia from Russia and then returned there, and it noted impact craters from stun grenades.

Kohver was reportedly trying to meet on September 5 with a Russian informant as part of an investigation into ties between Federal Security Service (FSB) agents, Russian criminal organizations, and smuggling operations across Russia's border into Estonia.

Estonian's internal security service, the Kaitsepolitsei (KaPo), is responsible for counterintelligence duties, as well as countering terrorism, protecting state secrets, and preventing the trafficking of weapons and radioactive material.

The European Union called repeatedly after the incident for Kohver's "immediate release," saying it was "concerned at the abduction" of Kohver "by the Russian security services on Estonian territory." Brussels called Russia's actions "against international law and the principle of inviolability of borders."

The United States called at the time for Kohver to be "safely" and "immediately" returned to Estonia by Russian officials.

The September 5 incident took place just two days after U.S. President Barack Obama visited Estonia, a NATO ally, to provide security guarantees in the face of rising tensions with Russia over Ukraine.

The tensions have included Moscow persistently probing NATO's defenses in the Baltic states and elsewhere along the alliance's eastern flank through cyberattacks, sea and airspace violations, and border incursions.

With reporting by Interfax, RIA Novosti