Popular microblogging site Twitter was briefly shut down overnight, its home page replaced with an image claiming the site had been hacked by the "Iranian Cyber Army."
The website's official blog acknowledged the disruption but gave no details as to how the site had been disrupted and who was responsible.
"Last night, DNS settings for the Twitter Web site were hijacked," the site's co-founder Biz Stone wrote Friday on the blog.
DNS stands for Domain Name System, an Internet protocol used to translate online addresses from long strings of numbers into simple "urls" such as www.twitter.com.
Hackers hijacked the settings for Twitter's website, rerouting about 80 percent of its traffic to another page from shortly before 0600 GMT until 0700 GMT, according to Stone.
"The motive for this attack appears to have been focused on defacing our site, not aimed at users," Stone wrote. "We don't believe any accounts were compromised."
Visitors were redirected from Twitter to a page with an image of a green flag under red text reading "Iranian Cyber Army" and "This site has been hacked by Iranian Cyber Army."
Screengrabs posted on Flickr clearly showed additional text below the image in English.
"U.S.A. Think They Controlling And Managing Internet By Their Access, But They Don't, We Control And Manage Internet By Our Power, So Do Not Try To Stimulation Iranian Peoples To," the text said in broken English.
"NOW WHICH COUNTRY IN EMBARGO LIST? IRAN? USA? WE PUSH THEM IN EMBARGO LIST. Take Care," it read.
Technology blog TechCrunch reported that the disruption also affected Google searches for Twitter.
It posted a screengrab showing that searches for a time returned a result reading "This Web Site Has Been Hacked by Iranian Cyber Army," above Farsi script.
"As an Iranian, in response to mischievous interference of this service provider at the order of US officials to meddle in our country's domestic affairs, this site is being hacked as a warning," the Farsi read, translated by AFP.
The hacker claimed to be in Iran, but people "tweeting" about the attack on Friday expressed skepticism.
Iranian demonstrators protesting the results of June presidential elections used Twitter extensively, both to organize marches and to release information about their movement.
The use of Web technology amid the Iran protests was closely watched in Washington, where a State Department official asked Twitter to postpone a planned maintenance shutdown by a day to allow Iranians to speak out and organize.
Their use of the microblogging site led some to dub the pro-democracy action against President Mahmoud Ahmadinejad a "Twitter revolution" and made the Iranian election one of the top "trends" on the site this year.
Israeli Prime Minister Benjamin Netanyahu earlier this month told the United States to use Twitter and other social networking sites to fight against the leadership of arch-enemy Iran.
"Iran prevents people from freely accessing the Internet," a senior official quoted Netanyahu telling parliament's foreign affairs and defense committee.
"Using the Internet and Twitter against the Iranian regime is something extraordinary that the United States can do," he said.
The microblogging sensation was back in action on Friday and apparently taking the attack in stride.
"Late night, early morning, big day, and a party to go to after work," Stone tweeted on Friday.