MOSCOW (AP) — A spokeswoman for Russian opposition leader Alexei Navalny says he has been detained outside his home in Moscow.

Kira Yarmysh said Navalny was detained early Saturday afternoon and taken to a nearby police station. She said she was not aware of the reason for his arrest.

Navalny, President Vladimir Putin's most formidable political foe, has called for nationwide rallies in early September to protest the Russian government's plans to raise the retirement ages for both men and women. The issue has outraged and united a wide range of people with different political backgrounds.

Moscow police were not immediately available for comment on the arrest.