A hacker group claimed credit Thursday for outages at Twitter after the company said it was affected by a "cascaded bug" which hit the wildly popular website.
"We just #TangoDown'd http://twitter.com for 40 minutes worldwide!" said a tweet from the group called UGNazi, which has been linked to attacks on US government websites.
The term "tango down" is sometimes used in the hacker community to refer to a so-called denial of service attack which can shut down a website.
The company first acknowledged "issues accessing Twitter," and said its "engineers are currently working to resolve the issue."
Around an hour later, Twitter said: "The issue has been resolved and all services are currently operational."
But after the problems resurfaced, Twitter said: "Today's outage is due to a cascaded bug in one of our infrastructure components."
The on-again-off-again access led to a barrage of comments and tweets about the problem, underscoring the growing importance of the messaging service.
"Twitters broke, my life has no meaning anymore," one user wrote on the social media website Tumblr.
Another wrote, "OMG TWITTER BROKE. I feel so alone right now."
Some tweeted their comments when the site was accessible.
"My boss shut down Twitter because he wanted me to get back to work. Feel free to kill him if you want," one tweet said.
Another said: "Twitter went down, I looked up & was like, who are these people in my house? Turns out I have a wife & a daughter."
And still another tweeted: "Unlike my ex-wife, Twitter came crawling back."
On Facebook, a member wrote: "Be honest. Did you spend most of Twitter being down desperately trying to tweet about Twitter being down?"
Twitter, which allows its members to post brief comments, links or pictures, claims to have more than 140 million active users, with the largest number being in the United States.
A recent survey found one in seven Americans who go online use Twitter and eight percent do so every day.