MOSCOW (Reuters) - Russian opposition leader Alexei Navalny has been detained in Moscow over his participation in an anti-government protest earlier this year, his spokeswoman Kira Yarmysh wrote on Twitter on Saturday.

Navalny was detained outside his Moscow apartment on Saturday afternoon for a reason that was initially unclear.

But after he spent a few hours at a police station, Yarmysh said Navalny had been detained over a brief appearance at a rally in Moscow in January that called for a boycott of the presidential election in March that he said would be rigged.

Navalny was not charged but his lawyer said at the time he would have to face court at a later date.

He had been planning protests on Sept. 9 against the Russian government’s unpopular plans to raise the pension age. The opposition leader was barred from running in the March election that President Vladimir Putin won in a landslide victory.

His spokeswoman said following his detention on Saturday, the 42-year-old was taken from the police station to hospital to treat a suspected fractured finger, an injury that he sustained when being detained.

Navalny, who has been jailed several times for organizing anti-Kremlin protests, will face a court hearing on Monday and will remain in custody until then, Yarmysh said.

He was last sentenced to 30 days in prison in May for his role in organizing nationwide protests against Putin.

He had called for demonstrations in more than 90 towns and cities under the slogan “Putin is not our tsar” to protest what he says is the Russian president’s autocratic rule.

Navalny said he was excluded from the election on a false pretext. Putin, 65, won his biggest ever election victory, extending his grip over Russia for six more years.