In a posting on piratebay.org, Anonymous claims to have stolen data from more than 100 websites in Turkey and replaced 74 government websites with protest messages.
The group indicated the action was part of a campaign by hackers, called Anti Security (AntiSec), to steal and leak classified government and company information to expose security flaws.
"Accessing and participating in the free flow of information is a basic human right. Anonymous will not stand by while the Turkish government violates this right. We will bring our support to circumvent censorship and retaliate against organizations imposing censorship," the message said.
Last month Anonymous carried out distributed denial of service (DDoS) attacks on some Turkish government websites in protest against the proposed filtering system the group alleges will make it possible to keep records of everyone's internet activity.
Turkish authorities responded by arresting 32 suspected Anonymous members purported to have been involved in the DDoS attacks.
Earlier this week, Anonymous claimed to have stolen 25 internal user names and passwords from Apple as part of its AntiSec campaign.
This story was first published by Computer Weekly