In its statement to users, Twitter said that it reset the pilfered passwords which had been hacked and sent users emails advising them that they will have to create a new one.
Twitter noted a recent surge in security breaches at several U.S. media and technology companies.
The New York Times and The Wall Street Journal reported this week that their computer systems had been infiltrated by China-based hackers.
Twitter says hackers may have gained access to information on around 250,000 of its more than 200 million active users.
More top news
Gunmen have attacked the Intercontinental Hotel in Kabul with casualties feared.
The Grammy-winning singer posted a picture of the two on his Instagram saying the two got engaged right before the new year.
British Airways said it was taking the matter "extremely seriously" and is assisting police with their enquiries.