Former world chess champion Garry Kasparov has been questioned by Russia's security service on suspicion of making extremist comments.
Garry Kasparov has become an outspoken opposition activist
Mr Kasparov, 44, is now an opposition activist and was briefly detained during recent protests against President Vladimir Putin.
He said he was being questioned because of comments made in a radio interview, but insisted he was not concerned.
Opposition protests in Moscow and in St Petersburg were broken up last weekend.
Hundreds of people were arrested during the marches, many of them followers of Mr Kasparov's opposition coalition, The Other Russia.
Mr Kasparov was reportedly in good spirits as he went for questioning at a security service building on Friday.
"The prosecutors are trying, through the FSB [security service], to detect traces of criminal acts in critical remarks about the authorities," the Reuters news agency quoted him as saying.
He defended his role as an opposition activist, which saw him arrested and fined at last weekend's protests.
"I think it's an important moment in Russia's political and public life and its jurisprudence because it's an obvious attempt to make any kind of political activity the subject of criminal law," he said.
According to a statement on Mr Kasparov's website, the FSB is questioning him over comments made in a radio interview and in a newspaper article ahead of the protests.
Mr Kasparov has said he will file complaints against the police for the protest arrests and insists his group's activities are protected by the Russian constitution.