Russian opposition leader Alexei Navalny was ordered Tuesday to spend 30 days in jail for staging an unsanctioned protest in Moscow and resisting police, charges he dismissed as unlawful.

Navalny organized a series of protests on May 5 in the Russian capital and other cities before President Vladimir Putin's inauguration for a new term. Demonstrations under the slogan "He is not our czar" took place throughout the country.

Moscow's Tverskoy District Court convicted Navalny on charges of organizing an unauthorized rally and ordered him jailed for 30 days. Separately, he was also convicted of disobeying police during the rally and sentenced to 15 days, but that sentence would be counted as part of the 30 days under Russian law.

Navalny argued that the authorities' refusal to allow the protest was illegal and called the accusations against him "ridiculous and unlawful."

The anti-corruption campaigner, who has become Putin's most visible political foe, already has served several weeks-long jail terms for organizing other protests.

The jail sentence could reflect the authorities' desire to keep Navalny behind bars to prevent him from staging more protests in the run-up to the World Cup hosted by Russia that could tarnish its opening on June 14.

Navalny tweeted from the courtroom that he was sentenced simply for "getting out on the street of my city and saying: 'I'm not your slave, and I will never be. I don't need a new Czar.'"

"There is nothing pleasant about the arrest, but I'm ready to come out and repeat it as many times as needed until we get what we want," he said. "And I know I'm not alone."