Tens of thousands demonstrators rallied in the Russian capital today in another massive protest against election fraud, signalling a growing outrage with Prime Minister Vladimir Putin's 12-year rule.

The demonstration in Moscow was as big as the one two weeks ago - the largest show of discontent the nation has seen since the 1991 Soviet collapse - although rallies in other cities in the far east and Siberia earlier today drew much smaller crowds.

Rally participants gathered on a broad avenue about 1.5 miles from the Kremlin on a snowy day.

A stage at one side of the avenue featured placards reading "Russia Will be Free" and "This Election is a Farce".

Recent protests in Moscow and other cities have dented Putin's authority as he seeks to reclaim the presidency in next March's vote. The Kremlin has responded by promising a set of political reforms that would liberalise election rules.

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

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

"People have come here because they want respect," said Tamara Voronina, 54, who said she was proud of her three sons who had also joined the protest.

The protests have reflected a growing public frustration with Putin, who ruled Russia as president from 2000-2008, and has remained the nation's number one leader after moving into the prime minister's seat due to a constitutional term limit.

Putin has accused the US of fomenting the protests in order to weaken Russia and 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 today held a picture montage of Putin with his head wrapped in a condom like a grandmother's headscarf.

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

He has promised to liberalise registration rules for opposition parties and restore the direct election of governors he abolished in 2004. Putin's stand-in President Dmitry Medvedev spelled out those and other proposed changes in Thursday's state-of-the nation address, promising to restore single-ballot 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 promises into law.

"These measures are insufficient," said Arina Zhukova, 45, another participant in the 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 presidential election and mounting a consolidated challenge to Putin in the March vote.

In another sign of authorities' efforts to stem a tide of public anger, the presidential human rights commission early today issued a statement condemning violations in the vote and backing protesters' calls for the ousting 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".

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