Former prime minister Kasyanov was denied registration as a presidential contender after the Central Election Commission (CEC) ruled that over 13% of the signatures collected to support his bid were either fake or unverifiable. His support team rejected the forgery claims as "political pressure."
Under Russian law, candidates not nominated by parliamentary parties have to collect at least 2 million signatures to support their application. The share of invalidated signatures cannot exceed 5% of the total.
Four candidates running for the Russian presidency include First Deputy Prime Minister Dmitry Medvedev, Communist leader Gennady Zyuganov, the ultranationalist Liberal Democratic Party leader Vladimir Zhirinovsky and Andrei Bogdanov, the leader of the tiny pro-Western Democratic Party.
Medvedev, who has been publicly backed by President Putin, is widely expected to win.
Two of Europe's main election monitoring bodies - the OSCE's Office for Democratic Institutions and Human Rights and the OSCE Parliamentary Assembly - refused earlier in February to send observers to the Russian polls, citing restrictions imposed by Moscow and saying the results are predestined.
The move, which came following weeks of wrangling over the size and scope of the monitor mission, is likely to further damage Russia's criticized democratic record.
Russia has accused the rights organization of bias and lacking coordinated standards.