Twitter users in Turkey report that the social media site has been blocked in the country.
Some users trying to open the twitter.com website are apparently being redirected to a statement by Turkey's telecommunications regulator.
It cites a court order to apply "protection measures" on the website.
This comes after PM Recep Tayyip Erdogan vowed to "wipe out Twitter" following damaging allegations of corruption in his inner circle.
The BBC's James Reynolds in Istanbul reports that he is unable to access Twitter.
"I don't care what the international community says at all. Everyone will see the power of the Turkish Republic," Mr Erdogan said earlier on Thursday.