Turkish authorities have blocked all access inside the country to Wikipedia.
According to officials, “an administrative measure” had been taken, but gave no reason why.
Turkish media said authorities had asked the online encyclopedia to remove content by writers “supporting terror”.
Turkey used to block social media sites, including Facebook and Twitter, for a period of time, usually following protests or terror attacks.
The Turkey Blocks monitoring group said Wikipedia was unreachable from 08:00 local time. People in Istanbul were unable to access any pages without using a Virtual Private Network (VPN).
Turkey’s Information and Communication Technologies Authority was quoted as saying: “After technical analysis and legal consideration based on the Law Nr. 5651 [governing the internet], an administrative measure has been taken for this website.”
It gave no further details.
However, the Hurriyet newspaper said Wikipedia had been asked to remove content by certain writers whom the authorities accuse of “supporting terror” and of linking Turkey to terror groups. Wikipedia had not responded to the demands, Hurriyet said, and the ban was imposed as a result.
Turkey Blocks and Turkish media, including Hurriyet, said the provisional order would need to be backed by a full court ruling in the next few days.
Social media was in uproar as news of the ban emerged, with some users speculating that it might be a bid to suppress criticism on President Recep Tayyip Erdogan’s Wikipedia page.
President Erdogan narrowly won a controversial April 16 referendum on increasing his powers, but the issue has deeply divided Turkey.
One Twitter user noted that the Wikipedia page on Turkey’s referendum has a section on “controversies and electoral misconduct”, and cites claims that the government suppressed the No campaign through “arrests, control of the media and political suppression”.
The Turkish government has previously denied censoring the internet, blaming outages on spikes in usage after major events.
Wikipedia has also faced censorship in other countries, including a temporary ban in Russia, and repeated crackdowns in China.