MOSCOW - International monitors said on Monday Russia's presidential election was clearly skewed to favor Vladimir Putin, a verdict that could spur protesters planning to take to the streets to challenge his right to rule.Putin, who secured almost 64 percent of votes on Sunday, portrayed his emphatic victory for a third term as president as a strong mandate to deal with the biggest anti-Kremlin protests since he rose to power in 2000. But vote monitors from the Organization for Security and Co-Operation in Europe watchdog echoed complaints by opposition leaders who said the election was not fair and who plan to protest against the outcome in central Moscow later on Monday."The point of elections is that the outcome should be uncertain. This was not the case in Russia," said Tonino Picula, one of the vote monitors. "According to our assessment, these elections were unfair."The OSCE monitors said Putin was given a clear advantage over his rivals in the media and that state resources were used to help him extend his domination of Russia for six more years.They called for all allegations of voting irregularities to be thoroughly investigated.Although the observers' findings have no legal bearing, they undermine Russian election officials' statements that there were no serious violations and confirm the concerns of many voters."It's not the people who choose, it's the authorities who choose themselves. It's all just a game put on for the people, an advertisement for Putin," said Agil Alekberov, who works in a Moscow home furnishings store.Putin's opponents, fearing he will smother political and economic reforms, have refused to recognise the result, which could allow the former KGB spy to rule Russia for as long as Soviet leader Leonid Brezhnev, accused of presiding over "the years of stagnation".Putin has already served as president or premier for 12 consecutive years and made way for his ally, Dmitry Medvedev, in 2008 only because of constitutional limits."He (Putin) is forcing things to breaking point. He is declaring war on us," said journalist Sergei Parkhomenko, one of the protest organisers.Monday's protest will take place within easy reach of the Kremlin and officials say the demonstrators could cause trouble by attempting to march towards the seat of power.Some protest leaders have received official warnings to be on their best behaviour from Moscow prosecutors.