WASHINGTON (AP) -- A group of hackers who breached the Senate's computer system this week claimed responsibility Wednesday for problems with the CIA's website.

The group, known as Lulz Security, tweeted ``Tango down - CIA.gov,'' and there were difficulties throughout the early evening accessing the agency's website.

The computer mischief appeared to have been targeting the CIA's public website, which includes no classified data and has no impact on the CIA's operation. CIA spokeswoman Marie Harf said the agency is looking into the reports.

It is sometimes difficult to tell whether a website has been hacked, or if the claim alone drove so many people to the site that it crashed. Efforts to access the website were met with an error message long after the breach began, around 6 p.m. EDT (1000 GMT).

Lulz has claimed responsibility for hacking into the systems of Sony and Nintendo and for defacing the PBS website after the public television broadcaster aired a documentary seen as critical of WikiLeaks founder Julian Assange.

On Monday, the group accessed a Senate server that supports the Senate's public website but did not breach other files, according to a Capitol law enforcement official. The hackers said the release was a ``just for kicks'' attempt to help the government ``fix their issues.''

Senate Deputy Sergeant-at-Arms Martina Bradford said in a statement that while the intrusion was inconvenient, it did not compromise the security of the Senate's network, members or staff.

Lulz Security claimed that it had added a Senate file to its list of successful, high-profile intrusions at a time when governments and corporations are on high guard for cyber intrusions.

The group has suggested it is trying to highlight cyber security weaknesses.