Twitter has experienced a major outage, with users across the world affected.
The company said there was no evidence that the outage was caused by a security breach or hack.
Users in countries including the US and UK were unable to use the platform for more than an hour. Some traffic has now been restored.
"We know people are having trouble Tweeting and using Twitter. We're working to fix this issue as quickly as possible," Twitter said.
According to DownDetector.com, reports of problems with Twitter began to spike at about 21:30 GMT.
Users were sent error messages including "something went wrong" and "Tweet failed: There's something wrong. Please try again later."