Microblogging website Twitter confirmed on Friday that unidentified hackers had accessed the website and obtained the data of up to 250,000 of its users.
The passwords and personal information such as email addresses of the users could have been found by the hackers, the company wrote in a blog post on its website on Friday.
"This week, we detected unusual access patterns that led to us identifying unauthorized access attempts to Twitter user data. We discovered one live attack and were able to shut it down in process moments later," the post read.
"However, our investigation has thus far indicated that the attackers may have had access to limited user information – usernames, email addresses, session tokens and encrypted/salted versions of passwords – for approximately 250,000 users."
The site followed the Wall Street Journal and the New York Times in being attacked this week but did not specify the circumstances of the attack, or its location.
The website, which has more than 200 million users worldwide, said it had automatically reset the passwords and contacted the users who had been affected.
Twitter also wrote that they did not believe the attack to be an isolated incident, nor was the hack the work of keen amateurs:
"The attackers were extremely sophisticated, and we believe other companies and organizations have also been recently similarly attacked. For that reason we felt that it was important to publicize this attack while we still gather information, and we are helping government and federal law enforcement in their effort to find and prosecute these attackers to make the Internet safer for all users," Twitter said.