Hacker group Anonymous is planning to reveal the identities of up to 1,000 Ku Klux Klan members, the latest twist in an ongoing cyber-war on the white supremacist group.

In Twitter messages and a YouTube video, the "hacktivist" collective said it had obtained the list of names from the Twitter account of a clan member.

"All will be revealed next month around the one year anniversary of #OpKKK," it tweeted, under the handle @Operation_KKK.

Anonymous took action against the Klan in November last year after members of the group threatened violence against peaceful protesters in Ferguson, Missouri.

The Midwestern town has become a symbol for racial tensions in America since the police shooting of an unarmed 18-year-old black man, Michael Brown, in August 2014.

In a statement earlier this week, Anonymous said it felt justified in "applying transparency" to the KKK.

"You are more than extremists. You are more than a hate group," the statement released online said.

"You operate much more like terrorists and you should be recognized as such. You are terrorists that hide your identities beneath sheets and infiltrate society on every level.

"The privacy of the Ku Klux Klan no longer exists in cyberspace. You've had blood on your hands for nearly 200 years."

The statement said: "We will release, to the global public, the identities of up to 1,000 Klan members, Ghoul Squad affiliates and other close associates of various factions of the Ku Klux Klan across the United States."

The Ghoul Squad is believed to be an auxiliary organization for KKK supporters.

Anonymous claimed to have taken down a KKK-linked Twitter account in November last year, and released the identities of a number of clan members.