U.S. authorities said on Monday they had arrested 10 suspected spies who had recruited political sources and gathered information for the Russian government.
"Such actions are baseless and improper," the Foreign Ministry said in a statement. "We do not understand what prompted the U.S. Justice Department to make a public statement in the spirit of Cold War espionage."
"We deeply regret that all of this has happened against the background of the relations reset declared by the U.S. administration," it said.
The individuals were accused of collecting information ranging from research programs on small-yield, high-penetration nuclear warheads, the global gold market and trying to obtain background on people who applied for jobs at the Central Intelligence Agency (CIA), according to criminal complaints filed in a U.S. federal court.
The Justice Department accused them of operating under orders of Russia's SVR agency as "illegals"; the term applied in the intelligence world to agents infiltrated to live and operate under false identities, rather than officers who use diplomatic cover or other legitimate cover.
Authorities said 10 of them were arrested on Sunday in Boston, New York, New Jersey and Virginia on charges including conspiracy to act as unlawful agents of the Russian Federation and money laundering.
Moscow has repeatedly accused Western powers of maintaining spying operations against Russia despite the end of the Cold War. Western powers also complain of Russian activity, especially in the commercial and scientific area.
BLOW TO OBAMA
The allegations come just days after Obama hailed a "reset" in ties between the former Cold War rivals when the two leaders met in Washington.
Medvedev last week toured the United States to try to show that Russia is building an innovative, investor-friendly economy. The U.S. Justice Department announced the arrests hours after Medvedev returned to Russia from a G20 summit in Toronto, which was also attended by Obama.
Russian analysts said the timing suggested it was an attempt by U.S. officials to undermine the reset, which Obama's administration has hailed as a major foreign policy achievement.
"It's is a slap in the face to Barack Obama," said Anatoly Tsyganok, a political analyst at Moscow's Institute of Political and Military Analysis. Russia will inevitably follow Cold War etiquette and uncover an equal number of U.S. spies, he said.
The chief spokesman for Prime Minister Vladimir Putin told Reuters he had no comment on the spying allegations and said the allegations were unlikely to be discussed during Putin's meeting on Tuesday with former U.S. President Bill Clinton in Moscow.
The chief spokesman for the SVR foreign intelligence service, Sergei Ivanov, said: "There will be no comment."
The goal of the alleged spies was to "become sufficiently 'Americanized' such that they could gather information about the United States for Russia and can successfully recruit sources who are in, or are able to infiltrate, United States policy-making circles," according to court papers.
One alleged spy was accused of sending back information about leadership changes at the CIA.
The U.S. Justice Department said they received extensive training in coded communications, how to evade detection and how to pass messages to other agents while casually brushing past them in public places.
The arrests are the culmination of a multi-year investigation that used extensive surveillance of communications and wiretaps, including putting listening devices into the homes of the accused individuals, the Justice Department said.