San Francisco: Twitter, the popular internet micro-blogging service, said it is fending off a cyber attack that prevented people from accessing its website for several hours on Thursday.
Twitter co-founder Biz Stone said on Twitter's blog that the site was the victim of a denial-of-service attack, a technique in which hackers overwhelm a website's servers with communications requests.
"We are defending against this attack now and will continue to update our status blog as we continue to defend and later investigate," Stone wrote.
A separate Twitter status web page said "the site is back up, but we continuing to defend against and recover from this attack." As of 10.30pm UAE time, the site was back up as normal.
Some people also reported delays logging in or posting to their Facebook profiles.
Facebook spokeswoman Brandee Barker said the company was looking into it and would have an update "as soon as possible."