Russian Facebook users have poured scorn on a promise by Russian President Dmitry Medvedev to investigate reports of electoral fraud.
At least 7,000 comments had appeared under his post by 20:00 GMT on Sunday, a day after the biggest anti-government protests since Soviet times.
An early random sample showed the comments were equally divided between hostility, support and neutrality.
Mr Medvedev prides himself on using social media.
He recently suffered an embarrassment on Twitter.
Having already conceded that some violations of electoral law had taken place at the parliamentary elections last Sunday, he went on Facebook to say he had issued instructions for all official reports on the conduct of the polls to be checked.
It was his comments on Saturday's election protests - some 50,000 people turned out in Moscow alone - which drew particular anger.
"I do not agree with either the slogans or statements heard at the rallies," Mr Medvedev wrote.
Facebook users pointed out that the chief, official slogan of the rallies had been "For Honest Elections".
Thousands of people have attended the biggest anti-government rally in the Russian capital Moscow since the fall of the Soviet Union.
As many as 50,000 people gathered on an island near the Kremlin to condemn alleged ballot-rigging in parliamentary elections and demand a re-run.
Other, smaller rallies took place in St Petersburg and other cities.
Communists, nationalists and Western-leaning liberals turned out together despite divisions between them.
The protesters allege there was widespread fraud in Sunday's polls though the ruling United Russia party did see its share of the vote fall sharply.
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The time has come to throw off the chains”
Jailed protest leader, in message posted on his blog
Demonstrations in the immediate aftermath of the election saw more than 1,000 arrests, mostly in Moscow, and several key protest leaders such as the anti-corruption campaigner Alexei Navalny were jailed.
A message from Mr Navalny was released through his blog, saying: "The time has come to throw off the chains. We are not cattle or slaves. We have a voice and we have the strength to defend it."
Prime Minister Vladimir Putin has never experienced popular protests like these before, the BBC's Steve Rosenberg reports from Moscow.
During his decade in power, first as president then prime minister, he has grown used to being seen as Russia's most popular and powerful politician.
But as one of the protesters put it to our correspondent, Russia is changing.
Milton Friedman and the Chicago School of Economics
eurozone members and others will adopt an accord with penalties for breaking deficit rules. It will be backed by a treaty between governments, not an EU treaty.
Moscow is braced for what the opposition claims will be the biggest demonstration in Russia for 20 years.
Tens of thousands are expected to gather in a square south of the Kremlin, in the latest show of anger over disputed parliamentary polls.
Smaller rallies are taking place in cities across the country.
The protesters allege Sunday's elections - which gave Prime Minister Vladimir Putin's ruling United Russia party a small lead - were fraudulent.
Hundreds of people have been arrested during anti-Putin protests over the past week, mainly in Moscow and St Petersburg.
At least 50,000 police and riot troops have been deployed in Moscow ahead of Saturday's protests.
The opposition says it is hoping for a turnout of 30,000 in the capital in the demonstration dubbed "For Fair Elections", due to begin at 14:00 (10:00 GMT).
Protests have already begun elsewhere, with several hundred marching in Vladivostok, seven timezones to the east of Moscow.
The BBC's Daniel Sandford in Moscow says in the past week, the city has resembled a police state rather than a democracy.
If the protests come even close to expectations, they will shake the 12-year-long political domination of Mr Putin, he says.
The authorities agreed to allow Saturday's demonstrations to go ahead following negotiations with opposition leaders.
The two sides reached a deal in which Moscow would allow a high-turnout if the rally was relocated from downtown Revolution Square to Bolotnaya Square, a narrow island in the Moscow River.
In St Petersburg, 13,000 people have pledged on the social networking site Vkontakte to take part in protests, with another 20,000 saying they might take part.
Authorities have granted permission for a demonstration in one location, but say protests anywhere else will be illegal and will be dealt with.
The top US military commander, Gen Martin Dempsey, says he is concerned about "the potential for civil unrest" as Europe's financial crisis unfolds.
Gen Dempsey said it was unclear the latest steps taken by EU leaders would be enough to hold the eurozone together, adding that a break-up could have consequences for the Pentagon.
Twenty-six of the 27 EU countries have agreed to forge a tighter fiscal union.
Only the UK refused to sign up to a new treaty, citing national interest.
Gen Dempsey, who is chairman of the Joint Chiefs of Staff, told an event hosted by the Atlantic Council, a Washington think-tank: "The eurozone is at great risk."
"I know that they've taken some measures here with the 17 members of the eurozone to try to better align... monetary and fiscal policy. But it's unclear, to me at least, that that will be the glue that actually holds it together."
Gen Dempsey previously served as the Army's Chief of Staff and as a general in Iraq.
He suggested that part of his concern was that the US military could be exposed to any unravelling of the eurozone "because of the potential for civil unrest and the break-up of the union".
The US military has more than 80,000 troops and 20,000 civilian workers in Europe, many based in Germany.
Gen Dempsey also said he was concerned that an international project to develop the F-35 Joint Strike Fighter aircraft could be put in jeopardy if European national defence budgets were cut.
"It will clearly put [budgets] at risk if all the economic predictions about a potential collapse were to occur," Gen Dempsey said.
At an emergency EU summit that ended in Brussels on Friday, the UK effectively used its veto to block an attempt, led by the French and Germans, to get all 27 members states to support changes to the union's treaties.
Instead, eurozone members and others will adopt an accord with penalties for breaking deficit rules. It will be backed by a treaty between governments, not an EU treaty.
The announcement on Friday produce little reaction from financial markets, which are still hoping for more intervention by the European Central Bank (ECB).
The BBC's Chris Morris says that without further action to lower the cost of borrowing, likely by the ECB, the eurozone still faces a threat.
The rising costs of borrowing in some eurozone countries have pushed governments to pass new austerity measures and to the International Monetary Fund as they struggle to pay their debts.
Europe's debt crisis has already unseated two political leaders and their governments: former Greek Prime Minister George Papandreou and Italian leader Silvio Berlusconi.