Story highlights Lawyer for detained Estonian security officer Eston Kohver says he's charged with spying

If convicted in a Russian court, he could face up to 20 years in prison, lawyer says

Estonia says the officer was abducted while on Estonian soil

Russia says it detained the security official in its northwest Pskov region

An Estonian security officer detained by Russia last week has been charged with espionage and could face up to 20 years in prison if convicted, one of his lawyers said Thursday.

Security officer Eston Kohver is currently in a detention center in Moscow, lawyer Mark Feygin told CNN over the phone.

Estonia summoned Russia's ambassador on Friday to demand an explanation regarding what it described as the abduction of a security official near the countries' joint border.

Russian officials say the Estonian was detained in Russia's northwest Pskov region, where they allege he was carrying out an undercover operation, according to a report from state-run news agency Itar-Tass.

The Estonian officer "had a Taurus handgun, an amount of €5,000 in cash, equipment for covert audio recording, and materials indicative of an intelligence mission," Itar-Tass reported, citing Russia's security service, the FSB.

The dueling claims follow mounting tensions between the two nations.

Only last week, U.S. President Barack Obama visited Estonia, where he promised that fellow NATO members would protect the Baltic nation against Russian aggression.

Foreign Minister Urmas Paet said Wednesday that Estonia considered Kohver's detention to be illegal and demanded his immediate return home.

He said two lawyers, one of them Feygin, had been appointed to represent Kohver in what he called an "extremely complicated situation."

On Thursday, UK Minister for Europe David Lidington raised "strong concern about the illegal and unacceptable abduction of an Estonian Security Service officer from Estonian territory by Russian Security Services" in a meeting with the Russian ambassador to London, the UK Foreign Office said.

He called for Kohver's immediate release.