The move to block the site of the Russian state news agency Sputnik in Turkey is an unlawful action and grave violation of fundamental human rights and freedoms, Russian foreign ministry said in a statement on Friday.
The website of Russian state news agency Sputnik has been blocked in Turkey, its Turkish editor-in-chief said, a move that could further strain relations between Moscow and Ankara after Turkey shot down a Russian warplane last year.
"There is no access to sputniknews.com and sub-domains from Turkey. We've sent a letter to the regulatory agency asking for the reasons. We were not expecting a ban at all," Mahir Boztepe told Reuters.
No one was available for comment at Turkey's telecoms and internet regulatory agency.
In a statement, Sputnik's top editor, Margarita Simonyan, described the blocking as "a further act of harsh censorship" in Turkey and said the site had been blocked late on Thursday, hours after Russian President Vladimir Putin made comments criticizing "some political leaders" in Turkey.
Relations between the former Cold War rivals hit their worst level in recent memory after Turkey shot down a Russian warplane over Syria in November, saying it had strayed into Turkish air space. In the Syrian civil war Moscow has backed its longtime ally, Syrian President Bashar al-Assad, while Turkey says Assad is a dictator who needs to be removed.
Following the warplane incident, Putin imposed sanctions on Turkey and trade between the two countries has dived.
Russian state media have adopted a hostile tone towards Ankara. Last month the Komsomolskaya Pravda mass-market tabloid ran a report headlined "Turkey never was and never will be a friend of Russia".
Human rights groups and some Turkish media decry what they say has been an unprecedented crackdown on opposition voices in Turkey.
Several opposition newspapers have been confiscated or closed in recent months and broadcasters taken off the air, accused of terrorist activities, while critical academics have been detained under broad anti-terrorism laws.