Russian authorities have detained the lawyer of opposition politician Aleksei Navalny's Anticorruption Foundation in Moscow.
Ivan Zhdanov wrote on Twitter on October 25 that police had detained him near a metro exit.
Navalny's spokeswoman Kira Yarmysh later tweeted that Zhdanov was taken to the Danilov district police department in the south of the capital.
No other details were immediately.
Zhdanov was detained in Moscow in May and later ordered to pay a fine for his alleged involvement in organizing nationwide protests against President Vladimir Putin.
Putin, who has been president or prime minister since 1999, was sworn in for a new six-year term on May 7 after a landslide victory in the election.
The vote was marred by allegations of fraud and what international observers said was a lack of a genuine choice.