WASHINGTON (Reuters) - The United States voiced "serious concerns" about Russia's parliamentary elections on Monday and called for a full investigation of what it said were credible reports of fraud.
"We have serious concerns about the conduct of those ... elections," White House spokesman Jay Carney said at a news briefing.
Several thousand people protested in Moscow against the election, which has been condemned by European monitors.
Prime Minister Vladimir Putin's party lost some of its dominance in the 450-seat Duma, where it was set to see its majority decline to 238 seats from 315 in the parliament, according to early forecasts.
Secretary of State Hillary Clinton, who has sought to consolidate improvements in sometimes strained U.S. ties with Moscow after a "reset" early in the Obama administration, said the United States was concerned by reports of stuffed ballot boxes, manipulated voter lists and other "troubling practices."
"Russian voters deserve a full investigation of all credible reports of electoral fraud and manipulation," Clinton said in Bonn, where she was attending an international conference on Afghanistan.
"The Russian people, like people everywhere, deserve the right to have their voices heard and their votes counted. And that means they deserve free, fair, transparent elections and leaders who are accountable to them. And we believe that that's in the best interests of Russia and we're going to continue to speak out about it."
State Department spokesman Mark Toner said Moscow should fully investigate charges laid by monitors sent by the Organization for Security and Cooperation in Europe electoral watchdog branch.
"The OSCE obviously has a follow-up mechanism in place to look at these as we go forward to see how they are addressed. That's the proper venue for that process," Toner told a news briefing.
"We believe that questions were raised by credible independent observers, and should be answered by an investigation."
He said the United States had spent more than $9 million on financial support and technical training for civil society groups before the election and would keep supporting those working to ensure free, fair and transparent electoral processes.
The Obama administration has repeatedly praised the results of the so-called reset in Russia ties, saying it had won progress on issues ranging from cutting nuclear arms to pressuring Tehran on its nuclear program.
But plans by Putin, known for his anti-U.S. rhetoric, to return to the presidency have raised concerns and the two sides are at odds over U.S. plans to set up an anti-ballistic missile shield to defend Europe against potential threats from Iran.
(Reporting by Matt Spetalnick, Arshad Mohammed and Andrew Quinn; editing by Christopher Wilson)