Twitter has admitted to have detected 'unusual access patterns' on its network this week suggesting that hackers may have gained access to information of approximately 250,000 users.

Though the micro-blogging Web site said it managed to shut down one live attack moments after it was discovered, there are chances that hackers may have possibly gained access to a number of data including usernames, email addresses, session tokens and encrypted/salted versions of passwords.

Twitter has immediately reset the passwords and revoked session tokens for the affected accounts and then informed the affected users (up to 250,000) through email notifications.

"As a precautionary security measure, we have reset passwords and revoked session tokens for these accounts. If your account was one of them, you will have recently received (or will shortly) an email from us at the address associated with your Twitter account notifying you that you will need to create a new password. Your old password will not work when you try to log in to Twitter," Twitter announced in a blog post.

Bob Lord, the director of information security at Twitter said the hacking attempt is not the work of amateurs and the company does not see the attack as an isolated incident. Twitter felt it's prudent to publicize the attack as it strongly feels this extremely sophisticated hack is similar to those recently reported attacks on a few other companies and organizations in the U.S. The sophisticated cyber attack comes on the heels of recent reports of long-term cyber infiltrations into some of leading U.S. media and technology companies, including The New York Times, The Washington Post and The Wall Street Journal. The New York Times later revealed that suspected Chinese hackers have managed to successfully access the usernames and passwords of all of its employees in an attempt to know the sources of their stories on the Chinese Prime Minister.

The social-networking giant advised its users to follow good password hygiene, on Twitter and elsewhere on the Internet. "Make sure you use a strong password - at least 10 (but more is better) characters and a mixture of upper- and lowercase letters, numbers, and symbols - that you are not using for any other accounts or sites. Using the same password for multiple online accounts significantly increases your odds of being compromised," the blog post said.