A Russian security service questioned a philosophy lecturer at Moscow State University on suspicion of extremism, local media reported Tuesday.
Vyacheslav Dmitriyev said he was questioned last week by the Federal Security Service (FSB), a KGB successor agency, the Slon.ru news website said.
He came under suspicion for reposting online an article about a possible regime change in Russia, he said.
"It was a hardline text, but I only posted it as a theoretically possible scenario," the scholar was cited as saying.
The FSB did not comment on the incident as of Wednesday morning.
Promoting extremism in Russia can be punished by up to three years in prison.
Dmitriyev, 54, has taught at Moscow State University since 1995, Colta.ru culture news website said. He made a name in academic circles by promoting post-structuralism in the 1990s and is currently active in the unregistered Pure Democracy Party, which advocates grassroots democracy.
Bloggers who republish others' material have faced extremism charges before.
In November, an opposition-minded blogger in western Siberia was slapped with a multimillion-ruble overdraft in his banking account after ending up on a state-run asset blacklist for retweeting a call to destroy corrupt officials' property.
The Venice Commission of the Council of Europe criticized Russian anti-extremism legislation in 2012 as too vague and having potential for politically motivated abuse.