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
At least two people have died after a strong earthquake in the Aegean Sea rocked Turkey and the Greek island of Kos.
The son Cecil the lion, whose 2015 killing prompted an international outcry, has also been fatally shot during a hunt.
Thickening cloud and rain stalling across Wales and southwest England through tomorrow