Twitter and Tweetdeck have gone down for some users after the social media giant suffered global outages.
"You might have trouble tweeting, getting notifications, or viewing DMs," the company said in a tweet on its own Support account.
"We're currently working on a fix, and should be back to normal soon."
It did not provide details about what caused the outage. However, on its API Status page, the company said it was investigating a "system irregularity".
Outage monitoring website Outage.report received more than 4,000 incident reports globally, including Japan, Canada and India.
Meanwhile Downdetector's outage map shows that users worldwide are reporting problems, with those in the UK, Japan, and the West Coast of the United States worst affected.
"Notifications aren't working, posts aren't working, polls are blank (not showing up at all), news and trending are empty …" wrote one user on the Downdetector forum.
"Can't send a new tweet on my TL. It's always 'you've already sent this tweet' – 'something went wrong' – 'some of your media failed to upload'," wrote another.
"My tweet keeps saying I already posted a duplicate tweet when I haven't :(" wrote another.
A Twitter representative earlier told Reuters that the company was investigating issues with TweetDeck, which was used by reporters and other content creators to monitor tweets from multiple Twitter accounts.
Log in attempts by TweetDeck users seem to be redirecting users to Twitter's website.
Here at Mirror Online, we are unable to upload pictures to Tweetdeck, and keep alerting messages about losing access to pages.