The Information and Communication Technologies Authority (BTK) has fined Twitter TRY 150,000 ($50,700 or roughly Rs. 33,97,000), the first time it has issued such a penalty to the company.
Despite repeated warnings, Twitter failed to withdraw content "praising terrorism, targeting the security forces and inciting hatred and violence", it said.
There were no further details on the nature of the offending content but Turkish officials have repeatedly expressed irritation over the presence of material on social media in favour of the outlawed Kurdistan Workers' Party (PKK).
The authorities have been waging a months-long crackdown on the PKK whose fighters have responded with deadly attacks on the Turkish security forces.
The authorities have repeatedly imposed temporary blocks on Twitter and other social media during times of crisis.
President Recep Tayyip Erdogan has a chequered relationship with Twitter, previously comparing social media to a "knife in the hand of a murderer" and saying "I don't like to tweet, schmeet."
But in February he started tweeting for the first time from his personal account @RT_Erdogan, which has now become one of his main communication platforms.
Erdogan's suspicion of social media dates back to the mass protests in June 2013 against his rule, which were largely mobilised by posts on Twitter and Facebook.
The government blocked Twitter and YouTube in March 2014 after they were used to spread a torrent of audio recordings implicating the prime minister and his inner circle in an alleged corruption scandal.
That ban on social media was later overturned by the country's top constitutional court.
In April this year, Turkey also blocked access to Twitter, Facebook and YouTube over the publication of images of a Turkish prosecutor killed by leftist militants during a hostage standoff.
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