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."
The hacker claimed to be in Iran, but people "tweeting" about the attack on Friday expressed scepticism.