Moscow wants answers after U.S. law enforcement officials arrested 10 people on Monday, who allegedly spied for Russia for up to a decade.
An 11th suspect, supposedly the money man of the operation was captured Tuesday, law enforcement officials said.
Assistant U.S. Attorney Michael Farbiarz on Monday called the allegations against the other 10 people living in the Northeast "the tip of the iceberg" of a conspiracy of Russia's intelligence service, the SVR, to collect inside U.S. information.
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The arrests threaten to tear apart what seemed to be a warming of relations between the Russian Federation and the U.S.
Russia's Foreign Ministry said in a statement Tuesday that the U.S. actions are unfounded and pursued "unseemly" goals.
Foreign Minister Sergey Lavrov pointed out that U.S. authorities announced the arrests days after Russian President Dmitry Medvedev visited the United States. Lawmakers suspect some of the suspects in the U.S. were attempting to weaken U.S.-Russian relations.
"They haven't explained to us what this is about," Lavrov said at a news conference during a visit to Jerusalem. "I hope they will. The only thing I can say today is that the moment for doing that has been chosen with special elegance."
The arrests came after Medvedev visited President Barack Obama at the White House last week. The two leaders exchanged jokes and went out for cheeseburgers to show that the two countries are working to rebuild relations.
The arrests were the result of a decade-long FBI investigation. The people who allegedly spied for Russia posed as innocent civilians while trying to learn about U.S. weapons, diplomatic strategy and politics.
Nikolai Kovalyov, the former chief of the main KGB successor agency, the Federal Security Service said that Russian-U.S. ties will continue to improve despite the spy scandal.
"Our two great powers must stand together," he said.