Russia's media watchdog accused the BBC Thursday of spreading the ideologies of "terrorist groups" via online publications of its Russian service, the latest in a tit-for-tat row over media impartiality.
Roskomnadzor, the state communications and media watchdog, said it would investigate whether the BBC was breaking the law.
This was the latest volley in a wave of rhetoric against the BBC, after Britain's broadcasting regulator Ofcom last year said the Moscow-funded RT channel had broken broadcasting standards.
"Currently we have discovered materials which transmit the ideologies of international terrorist groups (quotes of terrorist al-Baghdadi)" on the BBC's Russian language website, Roskomnadzor said in a statement.
Abu Bakr Al-Baghdadi is the leader of the Islamic state jihadist group, also known as ISIS.
Russian law does not forbid quoting individuals considered "terrorists", however any mention of such outlawed groups has to come with the disclaimer that the group is banned in Russia.
The watchdog said it would probe whether material broadcast by the BBC "corresponds with Russian anti-extremism legislation".
The BBC said in a statement sent to AFP that it "fully complies with the legislation and regulations of every country" in which it operates.