Citing online publication PC Magazine, RIA Novosti said the website was still offline.

"CIA TANGO DOWN: https://www.cia.gov/ #Anonymous," the hacker group wrote on Twitter.

Anonymous did not make public any details about the hacking, but the group's hackers normally use distributed denial of service (DDoS) attacks to knock their targets offline.

"We are aware of the problems accessing our website, and are working to resolve them," CIA spokeswoman Jennifer Youngblood told CNN Friday night.

Last month, Anonymous briefly took down the websites of the department of justice and the FBI in retaliation against the shutting down of the Megaupload file sharing website.