Vladimir Putin faces the largest demonstrations in Russia in 20 years as around 20,000 protesters prepare to take to the streets on Saturday.

The demonstrators say that elections last Sunday, which resulted in a small victory for Putin's United Russia Party, were fraudulent. A smaller protest, of around 8,000 people, followed the December 5 vote, and there have been other, fragmented shows of opposition in the regions, analysts said.

Some commentators have been quick to associate the rising tide of opposition to Putin's administration with the Arab Spring of popular movements that deposed autocratic regimes in the Middle East and North Africa, although some analysts believe that Putin's grip on power is too strong.

Putin, now prime minister, served the maximum two consecutive terms as president before handing over to Dmitri Medvedev in 2008. He has indicated that he will run for president again in elections in March 2012.

"Russia is unlikely to follow the path of Egypt or other nations that comprise the Arab spring. Putin still retains significant popularity, and Russia has $515 billion in reserves of which approximately $115 billion could be used for social spending," Eurasia Group analyst Cliff Kupchan wrote on Friday night.

"Moscow's security forces remain loyal, and in a crunch, at least elite troops would probably use force. Many Moscow elites are disgruntled but garner significant benefits from the government, while among the population apathy is reduced but appears to remain widespread."

Perhaps more importantly, Russia's demographics show less strain - the country has no "youth bulge" of restive under-25s, who formed the core of the opposition to leaders in Egypt, Tunisia and Libya, and its unemployment rates are relatively low.

As many as 50,000 riot police and security forces personnel have been deployed to Moscow ahead of the rally, which has been moved from the central Revolution Square to another plaza, Bolotnaya Square, which stands on an island accessible by a number of bridges. Protests are also being planned in other Russian cities.

How the protests pan out is uncertain, analysts said, as the government has not been reticent to arrest en masse in the past. An escalation, either in Moscow or in the regions, could be worrying for Putin.

"Moscow insiders believe that a turnout of 50,000 or more nationwide is possible and would embolden protestors and give momentum to the movement," Kupchan said. "The size of turnout in the regions will be key; a large turnout would establish the protest trend on a national level. To date, the regions have been quiet on broad political issues, and Putin retains significant popularity in many of them. If excessive force is used, and casualties result, political strains could become severe."