Russian opposition leader Navalny reports arrest

Russian opposition leader Alexei Navalny says he has been detained by police and that his chief of staff is also being held.

Navalny, who is President Vladimir Putin's most visible and vehement foe, said on his Twitter account that he was detained on Thursday after leaving a dentist's office. The reason was not immediately clear and there was no official confirmation.

Separately, Navalny relayed a tweet from chief of staff Leonid Volkov who said that he had been detained at a Moscow airport.

The anti-corruption campaigner has been repeatedly jailed for organizing unauthorized protest rallies throughout the country. He aimed to run for president in next month's election, but was denied a place on the ballot because of a fraud conviction that many view as politically motivated.