Paul Whelan, who was born in Canada but holds US, British and Irish citizenship, was arrested on Friday last week in Moscow "while carrying out an act of espionage", Russia's FSB domestic security service claims. The conversation was set up after he met with the US ambassador to Russian Federation.
The man, Dmitry Viktorovich Makarenko, was arrested on December 29 on the main island of Saipan in the Northern Mariana Islands, the ministry said Saturday in a statement.
While still a fugitive, Makarenko was indicted in June 2017 along with fellow Russian national Vladimir Nevidomy for money laundering and attempting to export defense-restricted goods - military grade night-vision rifle scopes, monoculars and ammunition primers - without obtaining the necessary licenses. The crimes were allegedly committed in 2013.
Makarenko, who was listed as a resident of Vladivostok, was declared a fugitive from USA justice in January 2018.
A Russian man has been arrested in a USA territory in the Pacific Ocean and transferred to the U.S. state of Florida, according to the Russian Foreign Ministry.
US Secretary of State Mike Pompeo said this week that Washington had asked Moscow to explain Mr Whelan's arrest and would demand his immediate return if it determined his detention is inappropriate.
"We should undergo all the procedures needed in this situation", Russian Deputy Foreign Minister Sergei Ryabkov told the Interfax news agency, Reuters reported. Ryabkov also warned Russians to "weigh the consequences of traveling overseas". The U.S.is leading the effort.
Ryabkov rebuffed those suggestions on Saturday. Whelan's lawyer, Vladimir Zherebenkov, has previously said he was charged on December 28, when he was arrested.
The United States is also now holding Maria Butina, a Russian citizen who pled guilty to espionage last month and co-operated with prosecutors over her attempts to infiltrate right-wing groups, including the National Rifle Association.
Britain cautioned Russian Federation on January 4 that individuals should not be used as diplomatic pawns.
Russian officials haven't given details of Whelan's suspected activities and he was initially identified only as an American.
Unlike in the U.S., Russia's holiday season runs into next week. He urged both the U.S. Congress and the State Department to help get his brother freed. The ambassador expressed support for Whelan and offered the embassy's assistance. Huntsman also spoke with Whelan's family by phone.
Russian Federation detained Whelan, 48, on charges of espionage on 28 December.
Speaking to the Press Association from Newmarket, Ontario, Mr Whelan's twin brother David said: "In the short-term the thing we would appreciate most from the UK Government and are certain that it's going to happen - we're not questioning any will on their part after Mr Hunt's statement - is that they will keep an eye on Paul and assist the USA and the other two countries to maintain him in good health until we can get him home".
"I'm pretty sure that some of the people he knows through social media are probably Russian soldiers because there are a lot of Russian soldiers and he probably knows one", David Whelan said in an interview.