By Alexei Anishchuk
MOSCOW (Reuters) - Russia's foreign ministry asked the United States on Thursday to explain why it had imposed sanctions on a well-known singer and supporter of President Vladimir Putin, calling the move "unacceptable".
The U.S. Treasury Department this week named Grigory Lepsveridze as one of six people it said were linked to a "Eurasian crime syndicate" called the Brothers' Circle.
The Treasury added him to its list of blacklisted people, meaning U.S. citizens were barred from doing business with him, and any assets he had in the United States were frozen.
Lepsveridze, who performs under the stage-name Grigory Leps, dismissed the allegation.
Russia's foreign ministry said Washington's accusation broke "the fundamental principle of presumption of innocence".
"We expect the U.S. authorities to provide detailed explanations," said Konstantin Dolgov, the ministry's human rights commissioner.
The U.S. Treasury said the six people had acted on behalf of two key members of the Brothers' Circle, which it described as a transnational criminal organization, a label shared with Japan's Yakuza and Mexico's Los Zetas syndicates.
"Grigory Lepsveridze couriers money on behalf of (Brothers' Circle member) Vladislav Leontyev," the Treasury said in a statement. A Treasury spokesman confirmed it was referring to the singer.
Lepsveridze, who publicly supported Putin during his last presidential campaign, said the accusations sounded like "raving" to him.
"I don't understand, which sanctions are threatening me?" he said on his website. "If they bar my entry, well, America is a great country, but I will live through it."
The U.S. Treasury statement said The Brothers' Circle was made up of leading members of several criminal groups, most of them based in former Soviet countries.
"The Brothers' Circle serves as a coordinating body for several criminal networks, mediates disputes between individual criminal networks, and directs member criminal activity globally," the Treasury added.
Relations between Moscow and Washington improved during U.S. President Barack Obama's first-term push to "reset" ties.
But they have deteriorated again amid disputes on Iran, Syria, human rights and Russia's decision to give temporary asylum to American fugitive spy contractor Edward Snowden.
(Reporting By Alexei Anishchuk; Additional reporting by Jason Lange in Washington; Editing by Andrew Heavens)