MOSCOW — The shot opens at the top of a flight of stairs and zooms in shakily on a gray-haired man, who sits at a desk furtively checking off what appear to be ballots — a stack of them.
The video is shot with the grain and chop of an amateur. But it is apparently sharp enough.
“A big hello to you,” says the cameraman, Yegor Duda, a 33-year-old volunteer election observer. “This is a violation of the criminal code. The chairman of the electoral commission is filling out ballots. Everything has been captured on the video camera,” he said.
“Mr. Duda is one of a number of freelance election observers in Russia, who, with the help of hand-held cameras and smartphones, have grown increasingly successful at frustrating voter fraud here.”
Mr. Duda raced home and uploaded the clip to YouTube. Though just three minutes long, it quickly became an election-day sensation, helping fuel a major demonstration of as many as 5,000 people on Monday evening in central Moscow. They chanted “Russia without Putin!” and “Putin is a thief.” Several hundred were arrested, including two major opposition leaders.
Valentin Gorbunov, the head of the Moscow City Elections Commission, confirmed the substance of the video and announced that Russian investigators had opened a case into ballot tampering by the head at Polling Place No. 2501, where the episode occurred, Russian news agencies reported Monday.
Election monitors from the Organization for Security and Cooperation in Europe said that they, too, had observed blatant fraud, including the brazen stuffing of ballot boxes. While the monitors declined to draw firm conclusions, it was clear from their report that vote stealing and other alleged malfeasance might have spared the presumed beneficiary, Prime Minister Vladimir V. Putin’s United Russia, an even worse blow than it officially received.
Secretary of State Hillary Rodham Clinton sharply criticized what she called “troubling practices” before and during the vote in Russia. “The Russian people, like people everywhere, deserve the right to have their voices heard and their votes counted,” she said in Bonn, Germany.
With 99.9 percent of ballots processed, election officials said that United Russia had won 238 seats in Parliament, or about 53 percent, from 315 seats or 70 percent now. The Communist Party won 92 seats; Just Russia, a social democratic party, won 64 seats and the national Liberal Democratic Party won 56 seats.
The scathing report by international observers, combined with the amateur video of alleged election malfeasance posted on the Web, made clear that the authorities would face continuing questions about the fairness of the vote despite the main party’s steep losses.
Indeed, on Monday evening, thousands of demonstrators gathered on a promenade by the Chistye Prudy metro station in central Moscow, and denounced the government at an event organized by the opposition group Solidarity. It was one of the largest such rallies in recent memory.
Throngs chanted “Russia without Putin!” and “Putin is a Thief.” Police officials estimated the crowd at about 2,000 though some participants said it was larger. There was a presence of police officers in riot gear and some protesters were detained.
Mr. Duda’s video was just one of several clips putatively documenting violations to go racing through the Internet during parliamentary elections on Sunday, a relatively new weapon in the fight against vote rigging that has begun to expose Russians to the realities of their electoral system like never before.
“To be honest, I didn’t expect there to be any violations. I hoped there wouldn’t be,” Mr. Duda, who had never been an election observer before, said in a brief telephone interview. “I now understand better what goes on there. And as long as I think it will be useful, I will continue to tell people about what is happening.”
Mr. Duda is one of a number of freelance election observers in Russia, who, with the help of hand-held cameras and smartphones, have grown increasingly successful at frustrating voter fraud here.
It is not clear whether this tactic will ever succeed in changing the conduct of elections in Russia. With many of the videos apparently showing violations by United Russia, officials on Monday moved quickly to discount them.
“I’ve seen these clips people are uploading to the Internet,” Russia’s president, Dmitri A. Medvedev, said. “Nothing can be seen in them.”
But many of the millions of Russians who have watched the videos seem convinced that they are witnessing fraud.
In another video from Moscow, observers from the opposition Yabloko party demonstrated that the ink in pens supplied in voting booths at one polling place on Sunday was easily erasable.
Another showed packets of ballots apparently just removed from the ballot box, stacked neatly, one on top of the other, an indication that they were inserted together, not individually. All were marked for United Russia.
Among the most widely circulated videos was one shot by amateur cameramen accompanying journalists and other election observers who had reportedly infiltrated a group hired to stuff ballot boxes in Moscow. Caught with multiple ballots marked for United Russia in bags they wore under their clothes, some involved in the plot tried to flee. The video showed the police stopping them at the doors.
Andrei Kursov, a 24-year-old employee of a tobacco company, helped record the episode. Speaking by telephone, he said the police at the polling place were initially aggressive to the observers and unwilling to take action against the violators. One threatened to beat him over the head if he refused to stop recording, he said.
“The law enforcement agencies typically try not to pay attention to violations,” Mr. Kursov said. “But with the camera there, they were probably afraid this time that if they let these guys go they would get in trouble.”
Such videos have appeared in the past, but this seems to be the first election in which the tactic was put to such widespread and effective use. Even the international observers from the O.S.C.E. praised the work of amateur election monitors.
“We saw in the campaign before the elections all sorts of possible tricks being shown and displayed on the Internet,” said Ambassador Heidi Tagliavini, the head of the election observation mission of the group’s Office for Democratic Institutions and Human Rights. “This was, I would say, a new feature.”
Glenn Kates contributed reporting from Moscow, and Steven Lee Myers from Bonn, Germany.