Twitter has told employees that the company's office buildings will be temporarily closed, effective immediately. It did not give a reason for the move.
The announcement comes amid reports that large numbers of staff were quitting after new owner Elon Musk called on them to sign up for "long hours at high intensity" or leave.
Announcement that Twitter had temporarily closed its offices came amid signs that large numbers of workers have now also resigned as they have not accepted Mr Musk's new terms.
Employees have been tweeting using the hashtag #LoveWhereYouWorked and a saluting emoji to show they were leaving the firm.
Musk, also the CEO of Tesla and SpaceX, has come under fire for radical changes at the social media company, which he bought for $44 billion late last month.