Twitter has been knocked offline for several hours due to an ongoing denial of service attack.
It's not clear when the outage started, but reports on the outage surfaced around 14:00 BST, with many users finding themselves unable to access the micro-blogging platform.
A notice on Twitter's status blog stated: "We are defending against a denial-of-service attack, and will update status again shortly."
The status blog lets users know about planned or unplanned outages and other issues on Twitter.
A report on Wired.com said that attempts to access the Twitter site or the Twitter blog through Google were blocked, and the journalist was greeted with an error message beginning “We’re sorry… but your query looks similar to automated requests from a computer virus or spyware application. To protect our users, we can’t process your request right now.”
But Computerworld UK was able to access the Twitter blog through Google.
The current outage is one of the longest in recent months, according to TechCrunch. Back in 2007 and 2008, Twitter downtime was relatively frequent: this year the site has been far more stable and its early outages have been largely forgotten.
"On this otherwise happy Thursday morning, Twitter is the target of a denial of service attack. Attacks such as this are malicious efforts orchestrated to disrupt and make unavailable services such as online banks, credit card payment gateways, and in this case, Twitter for intended customers or users. We are defending against this attack now and will continue to update our status blog as we continue to defend and later investigate.
On the Twitter status site, the engineers claim that "the site is back up" however Computerworld UK and many other users are still unable to access the platform.