Many users in Turkey were unable to access Twitter on Saturday, the social networking site said, after at least 86 people were killed in the capital Ankara in suspected twin suicide bombings.
It was not immediately clear if the problem was related to the attack, but the Turkish government has moved before to block or limit social media sites -- including Twitter -- at sensitive times, prompting accusations of censorship.
"Users in Turkey are reporting issues accessing Twitter in many areas. We're investigating and hope full service will be restored soon," Twitter's @policy account tweeted in English and Turkish.
In July, a Turkish court ordered a ban on publishing images of a deadly suicide bombing near the border with Syria on all print, visual and online media, including Twitter.
President Recep Tayyip Erdogan and his Islamic-rooted ruling Justice and Development Party (AKP) have been repeatedly criticized over curbs on social media.
Turkey's parliament in April approved legislation to tighten control over the Internet by allowing the government to block websites without prior judicial authorization.
The government blocked Twitter and YouTube in March 2014 after they were used to spread a torrent of audio recordings implicating Erdogan -- then premier -- and his inner circle in an alleged corruption scandal.