Vladimir Putin's party won a crushing victory in parliamentary elections, paving the way for the authoritarian leader to remain in control even after he steps down as president.
"The vote affirmed the main idea: that Vladimir Putin is the national leader, that the people support his course, and this course will continue," party leader and parliament speaker Boris Gryzlov said after exit polls were announced.
Several opposition leaders accused the Kremlin of rigging the vote, and U.S. President George W. Bush's administration called for a probe into voting irregularities. Communist Party leader Gennady Zyuganov called the election "the most irresponsible and dirty" in the post-Soviet era and party officials vowed to challenge the results.
Turnout was about 62 percent, up from 56 percent in the last parliamentary elections four years ago.
The Kremlin portrayed the election as a plebiscite on Putin's nearly eight years as president - with the promise that a major victory would allow him somehow to remain leader after his second term ends next year.
Putin is constitutionally prohibited from running for a third consecutive term, but he clearly wants to stay in power. A movement has sprung up in recent weeks to urge him to become a "national leader," though what duties and powers that would entail are unclear.
Pollsters said United Russia's performance would give it an overwhelming majority of 306 seats in the 450-seat State Duma, or lower house. The Communists would have 57 seats.
Two other pro-Kremlin parties - the nationalist Liberal Democratic Party and populist Just Russia - also appeared to have made it into parliament, with 8.2 percent and 7.6 percent, respectively.
One Liberal Democratic Party deputy will be Andrei Lugovoi, a former KGB officer and chief suspect in the poisoning death of Kremlin critic Alexander Litvinenko in London last year. Russia has refused to hand Lugovoi over to Britain, and the Duma seat provides him with immunity from prosecution.
No other parties passed the 7 percent threshold for gaining seats in the legislature. Both opposition liberal parties were shut out, predicted to win no more than 2 or 3 percent of the vote each.
Many Russians complained Sunday about being pressured to cast their ballots, with teachers, doctors and others saying they had been ordered by their bosses to vote.
"People are being forced and threatened to vote; otherwise they won't get their salaries or pensions," said Boris Nemtsov, leader of the liberal Union of Right Forces party.
Dozens of voters reported being paid to cast ballots for United Russia, said Alexander Kynev, a political expert with election monitoring group Golos. In the town of Pestovo in the western Novgorod region, voters complained they were given ballots already filled out for United Russia, he said.
In Chechnya, where turnout was over 99 percent, witnesses reported seeing election authorities filling out and casting voter ballots in the suburbs of the regional capital, Grozny.
There was a tense, subdued mood at some polling stations. Yelena, a 32-year-old manager in St. Petersburg, refused to give her last name out of fear of official retaliation for voting for the liberal Yabloko party.
"We live in a country with an absence of democracy and freedom of speech," she said.
Many voters were reluctant to discuss their vote - a shift since the late 1980s, when Russians complained loudly about their government. One elderly woman, a veteran of a defense research institute, refused to give her name and only admitted that she had voted for Yabloko when she was certain no one else was listening.
The Kremlin appeared determined to engineer a resounding victory. But Putin, credited with rebuilding Russia after the poverty and uncertainty of the 1990s, has support from many Russians.
"Today everything is clear and stable in life. The president's words always coincide with what he does. As for the other candidates we don't know yet where they would take us to," said Raisa Tretyakova, a 61-year-old pensioner in St. Petersburg.
The Bush administration called on Russia to investigate claims the vote was manipulated.
"In the run-up to election day, we expressed our concern regarding the use of state administrative resources in support of United Russia, the bias of the state-owned or -influenced media in favor of United Russia, intimidation of political opposition, and the lack of equal opportunity encountered by opposition candidates and parties," said Gordon Johndroe, spokesman for the National Security Council.
All seats will be awarded according to the percentage of the vote each party receives; in previous elections, half the seats were chosen among candidates contesting a specific district, allowing a few mavericks to get in . About 109 million people are eligible to vote.
The Organization for Security and Cooperation in Europe, regarded in the West as the most authoritative election monitor, canceled plans to send observers.
Putin claimed the pullout was instigated by the United States to discredit the elections. But the OSCE said Russia delayed granting visas for so long that the organization would have been unable to meaningfully assess election preparations.