The agency`s Turkish staff said no warning had been received from telecoms authorities.
Relations between Moscow and Ankara have worsened since Turkey shot down a Russian warplane near the Syrian border five months ago.
The news comes hours after a series of anti-Turkish statements from Russian President Vladimir Putin in the course of his annual televised phone-in.
Sputnik was launched by Russian state media in 2014 to target a global audience "who want a different perspective".
"We`ve sent a letter to the regulatory agency asking for the reasons," editor-in-chief Mahir Boztepe told Reuters news agency. "We were not expecting a ban at all."
Controversial legislation introduced in 2014 gave Turkish authorities the power to block websites for privacy violations without a court decision.
President Recep Tayyip Erdogan has been accused of presiding over an increasingly authoritarian administration.
Last month Turkey`s biggest newspaper, Zaman, was taken over by the authorities after a court ruling placed it under state control. No explanation was given for the ruling.
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