Wikipedia has been blocked due to its articles and comments showing Turkey in coordination and aligned with various terrorist groups, said an email statement by the Transport, Maritime Affairs and Communications Ministry.
"Instead of coordinating against terrorism, it has become part of an information source which is running a smear campaign against Turkey in the international arena," said the ministry.
Ankara warned it to remove the offending content but the nonprofit encyclopedia refused, it added.
It said the access ban would be lifted if Wikipedia meets Turkey's demands.
Turkey has requested that such websites take such steps as having a representative in the country, complying with principles of international law, implementing court rulings, and not being part of any smear campaign or operation in Turkey.