Tens of thousands protested in Istanbul in May against Internet censorship and plans for a new filtering system, due to be introduced on Aug. 22, under which users must sign up for one of four filters -- domestic, family, children and standard.
The Information and Communication Technologies Authority says there will be no difference between the standard filter and the current system, but that the other filters would offer the option to restrict access for those who wanted it.
Anonymous said the filtering system would make it possible to keep records of people's Internet activity.
"Though it remains opaque why and how the system will be put in place, it is clear that the government is taking censorship to the next level," the statement said.
"We will bring our support to circumvent censorship and retaliate against organisations imposing censorship."
In response, a group of nationalist Turkish hackers said on the ayyildiz.org website they had launched a retaliatory strike against Anonymous sites.
"The issue is not censorship, it is betrayal of the nation," the statement said.
Turkey has previously banned access to various websites, including YouTube for a period of more than two years, under court orders imposed for infringing decency laws.
In December, Anonymous launched attacks that temporarily shut down the sites of MasterCard Inc and Visa Inc using simple software tools available over the Internet.
It attacked them with denial-of-service attacks that overwhelmed their servers for blocking payments to WikiLeaks.
Last month it denied responsibility for a cyber-attack on Sony Corp's networks that exposed the personal data of more than 100 million video gamers.