Opposition leaders and rights activists on Wednesday presented fresh indications of massive fraud at last Sunday's parliamentary vote, insisting that election officials fabricated 20 percent to 25 percent of United Russia's result.
But Central Elections Commission head Vladimir Churov said evidence of the fraud had been fabricated, though he gave no details.
If ballots were counted accurately, United Russia's share would have been just under 30 percent instead of 49 percent, the Citizen Observer movement said.
At a news conference Wednesday, organizers of the group, which includes members of the Memorial human rights organization and the Golos election watchdog, presented a web site, which charts results based on 300 volunteers that collected data from 800 ballot stations throughout the country.
By late Wednesday, the site contained data from 102 stations and said United Russia's real share stood at 29.8 percent.
In a separate briefing, leaders of the liberal Yabloko party, which officially got 3.4 percent of the vote, told reporters that more half of their votes were stolen and that United Russia's real result was just 25 percent.
"The longer you look at these elections, the less they seem like elections," party chairman Sergei Mitrokhin said.
An analysis of 3,000 polling stations in the city showed that falsification was widespread and systematic, he said.
Yabloko's co-founder Grigory Yavlinsky, who headed the party's Duma list, accused the Kremlin of conspiring to halve its number of votes.
He put the number of votes for his party at close to 5 million before electoral manipulation.
According to the official preliminary results, Yabloko got 2.25 million votes, or 3.4 percent of the total.
Yavlinsky also said the success of the Duma's two leftist opposition parties showed the Kremlin's desire to take a populist turn in 2012.
The Communists and A Just Russia significantly increased their share of the vote to 19 percent and 13 percent, respectively, according to the official result.
Mitrokhin announced that Yabloko would challenge the vote in court and is planning a protest rally in the city on Dec. 17 to demand Churov's removal.
"We need no wizards in this post," he told reporters.
On Tuesday, President Dmitry Medvedev praised the elections chief during a meeting as being "almost a wizard" because he had predicted voter turnout at 60 percent, missing the result of 60.2 percent by just 0.2 percentage points.
Churov replied that he was "still learning," according to a Kremlin transcript.
The head of the elections commission is widely reviled by the opposition as a Kremlin stooge to organize and cover up fraud.
But in an interview published Wednesday, Churov hit back at some of the criticism by alleging that videos showing vote-rigging had been fabricated.
"I knew already before election day that false polling stations had been set up in apartments to shoot films. I believe we will see more of this," he told the Itogi weekly.
Churov went on to say ballot box-stuffing, another widely alleged fraud method, was impossible because it would take too much time to fill boxes with significant numbers of ballots.
Members of the Citizen Observer group, however, presented fresh reports about violations on Wednesday.
In Moscow's Sokolniki district, the head of the local elections committee dived headfirst into a ballot box during the vote count in an apparent attempt to evenly distribute stacks of ballots, group coordinator Mikhail Shnaider said.
"He was practically swimming in the box so that just his feet were visible," he recalled at the group's news conference.
The stunt was not successful as observers later found ballot bundles held together by string with checks for United Russia, Shnaider said.
Another observer for the group, Nikolai Pismenny, minutely described on his web site with photos and videos Wednesday how elections commission members in Polling Station 2744 in the Fili-Davydkovo district in the city's west altered the result of the vote count during lengthy calculations and repeated phone calls with unidentified persons.
The elections were also monitored by some 700 foreign observers, including some 350 from European watchdogs.
The missions from the Organization of Security and Cooperation in Europe, or OSCE, and the Council of Europe on Monday criticized the elections as only partially free and fair.
The Foreign Ministry issued an angry reply to this Wednesday, saying the watchdogs' criticism was politicized and not objective, and even suggesting that foreign observers had no right to judge national elections.
"We assume that elections are first and foremost held in the interest of Russian citizens and that it is they who have the right to issue a final judgment about the voting," the Ministry said in a statement on its web site.
The European Union said in a first reaction that the reports about violations raised serious concerns.
"I expect that the issues … will be addressed by Russian authorities to allow for smooth and fair presidential elections in the spring," EU foreign policy chief Catherine Ashton said in an e-mailed statement Wednesday.
Meanwhile, former Soviet leader Mikhail Gorbachev echoed the opposition by calling for the vote to be annulled.
Gorbachev told Interfax in an interview that authorities must hold fresh elections or deal with a rising tide of discontent.
"More and more people are starting to believe that the election results are not fair," he was quoted as saying. "I believe that ignoring public opinion discredits the authorities and destabilizes the situation."
Neither the Kremlin nor the government commented on Gorbachev's call, but Medvedev has said the vote was "just, fair and democratic" and that United Russia got the amount of votes it deserves.