Twitter suffered a major outage on Wednesday evening, leaving tens of thousands of users globally unable to access the popular social media platform or use its key features for several hours before services appeared to come back online.
The incident is the social media site's first apparent widespread service disruption since billionaire Elon Musk took over Twitter as CEO in late October.
Downdetector, a website that tracks outages through a range of sources including user reports, showed more than 10,000 affected users from the United States, about 2,500 from Japan and about 2,500 from the UK at the peak of the disruption.
Most of the reports came from users stating they faced technical issues accessing the social network via a web browser.
Reports of Twitter outages fell sharply by Wednesday evening, according to the website, with some users later commenting service had returned to normal.
Twitter did not immediately respond to a request for comment and the social network's status page showed that all systems were operational.
Musk tweeted later on Wednesday that "significant backend server architecture changes" had been rolled out and that "Twitter should feel faster," but his post did not make any reference to the downtime reported by users.
During the outage, some users said they were unable to log in to their Twitter accounts via desktops or laptops. A smaller number of users said the issue also affected the mobile app and features including notifications.
Others took to Twitter to share updates and memes about the service disruption, with #TwitterDown trending as a hashtag on the social media site.
Some attempts to log in to Twitter from desktops prompted an error message saying: "Something went wrong, but don’t fret - it’s not your fault. Let’s try again."
Musk tweeted he was still able to use the service.
"Works for me," Musk posted, responding to a user who asked if Twitter was broken.
The outage comes two months after Musk completed his $44 billion (€41 billion) takeover of Twitter, which has been marked by chaos and controversy.
Hundreds of Twitter employees quit the social media company in November, by some estimates, including engineers responsible for fixing bugs and preventing service outages.
Thousands of Twitter users were also hit by global outages in February and July, before Musk's takeover.
Other big technology companies have also been hit by outages this year. In July, a nearly 19-hour service outage at Canada's biggest telecom operator Rogers Telecommunications shut banking, transport and government access for millions.