|Analysts downplayed the significance of the attacks, saying hackers are just looking to show off [GALLO/GETTY]
The Hacker group Lulz Security claims it briefly brought down the public site of the US Central Intelligence Agency CIA).
The US spy agency's cia.gov website stopped responding on Wednesday and members of the group claimed credit in a message on Twitter at @LulzSec.
"Tango down - cia.gov," the message read. "For the lulz".
Lulz, whose members are strewn across the globe, announced the attack shortly before 1800 US east coast time.
Marie Harf, a CIA spokeswoman, said the agency was looking into the reports.
Attempts by the AFP news agency to reach cia.gov were met with a message saying the web page was not available.
The website initially could not be accessed from New York to San Francisco, and Bangalore to London.
Later in the evening, service was sporadic. Cia.gov was back online within two hours.
Lulz Security has claimed in recent weeks to have staged attacks on the online operations of Sony, Nintendo, the US Senate, the US Public Broadcasting System news organisation and Infragard, a company that works with the FBI.
The hacker group has defaced websites, posted personal information about customers and site administrators, and disclosed the network configurations of some sites.
Security analysts have downplayed the significance of these attacks, saying the hackers are just looking to show off and get as much attention as possible.
On Monday, Lulz Security 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.
Elsewhere, another group advocating Internet freedom - the so-called DragonForce Crew - attacked Malaysian government websites, including the tourism ministry's website, which they defaced.
Several other Malaysian government sites went offline for several hours, but most later returned to normal.