Tens of thousands of demonstrators on Saturday cheered opposition leaders and jeered the Kremlin in the largest protest in the Russian capital so far against election fraud, signalling growing outrage over Prime Minister Vladimir Putin's 12-year rule.

The demonstration in Moscow was even bigger than a similar protest two weeks ago, although rallies in other cities in the far east and Siberia earlier in the day drew smaller crowds than on Dec. 10. The demonstrations are the largest show of discontent the nation has seen since the 1991 Soviet collapse.

Rally participants densely packed a broad avenue, which has room for nearly 100,000 people, about 2.5 kilometres from the Kremlin, as the temperature dipped well below freezing. They chanted "Russia without Putin!"

A stage at the end of the 700-metre avenue featured placards reading "Russia will be free" and "This election Is a farce." Heavy police cordons encircled the participants, who stood within metal barriers, and a police helicopter hovered overhead.

Alexei Navalny, a corruption-fighting lawyer and popular blogger, electrified the crowd when he took the stage and had protesters shouting "We are the power!"

Navalny spent 15 days in jail for leading a protest the day after the Dec. 4 parliamentary election that unexpectedly drew more than 5,000 people and set off the chain of demonstrations. Since his release, he has helped to further galvanize the opposition.

Putin's United Russia party lost 25 per cent of its seats in the election, but hung onto a majority in parliament through what independent observers said was widespread fraud. United Russia, seen as representing a corrupt bureaucracy, has become known as the party of crooks and thieves, a phrase coined by Navalny.

Maintaining momentum key

The recent protests in Moscow and other cities have dented Putin's authority as he seeks to reclaim the presidency in a March vote. The Kremlin has responded by promising a set of political reforms that would allow more political competition in future elections.

But protest leaders say they will continue pushing for a rerun of the Dec. 4 parliamentary election and punishment for officials accused of vote fraud. They say maintaining momentum is key to forcing Putin's government to accept their demands.

'A thief must not sit in the Kremlin'—Boris Nemtsov, opposition leader

"We don't trust him," opposition leader Boris Nemtsov told the rally, urging protesters to gather again next month to make sure that the proposed changes are put into law. Along with liberals, the rally also drew communists, nationalists and other groups.

Nemtsov called on the demonstrators to go to the polls in March to unseat Putin. "A thief must not sit in the Kremlin," he said.

"We want to back those who are fighting for our rights," said 16-year-old Darya Andryukhina, who said she had also attended the previous rally.

The protests reflect a growing public frustration with Putin, who ruled Russia as president in 2000-2008 and has remained the No. 1 leader after moving into the prime minister's seat due to a constitutional term limit.

"No one has done more to bring so many people here than Putin who managed to insult the whole country," said Viktor Shenderovich, a columnist and satirical writer.

But the protesters have no central leader and no candidate capable of posing a serious challenge to Putin, who intends to return to the presidency in March. Even at Saturday's rally, some of the speakers were jeered by the crowd.

Putin has accused the United States of fomenting the protests in order to weaken Russia and has said, sarcastically, that he thought the white ribbons many protesters wear as an emblem were condoms.

In a response to Putin's blustery rhetoric, one protester Saturday held a picture montage of Putin with his head wrapped in a condom like a grandmother's headscarf.

Reform measures 'insufficient'

Although Putin has derided the demonstrators as Western stooges, he has also sought to soothe public anger by promising to relax his grip on the political scene.

He has promised to liberalize registration rules for opposition parties and restore the direct election of governors he abolished in 2004. Russian President Dmitry Medvedev, spelled out those and other proposed changes in Thursday's state-of-the nation address, promising to restore direct elections to fill half of the seats in parliament and ease rules for the presidential election.

Some opposition leaders welcomed the proposals, but stressed the need for the protests to continue to force the Kremlin to quickly turn the promises into law.

"These measures are insufficient," said Arina Zhukova, 45, another participant in Saturday's rally. "They are intended to calm people down and prevent them from showing up at rallies."

The electoral changes, however, will only apply to a new election cycle years away, and the opposition has stressed the need to focus on preventing fraud in the March presidential election and mounting a consolidated challenge to Putin.

In another sign of the authorities' efforts to stem the tide of public anger, the presidential human rights commission early Saturday issued a statement condemning violations in the vote and backing protesters' calls for the ouster of Central Election Commission chief Vladimir Churov.

It said that allegations of widespread fraud have led to a "moral and political discrediting of the election system and the lower house of parliament, creating a real threat to the Russian state."