A hacker says he gained access to "the entire database of users on Twitter" and has already leaked the account details of more then 15,000 accounts online.

A hacker under the name Mauritania Attacker — who claims to be from Mauritania, a country in West Africa, and says he hacks sites in the name of Islam — shared details on Tuesday about the leak via file-sharing site Zippyshare, according to a GigaOm report. The information includes every account's Twitter name, ID and authentication tokens associated with third-party apps that have access to the account (for example, Instagram or HootSuite). Passwords were not leaked.

"We have investigated the situation and can confirm that no Twitter accounts were compromised," a Twitter spokesperson told Mashable.

The news comes after Twitter sent an email late Monday to verified users urging them to use two-step authentication to keep accounts secure.

"With a highly visible account like yours, it's a good idea to be extra careful," the email read. "Login verification is a simple way to add more protection to your account."

A source close to the matter also told Mashable the issue involved a specific third-party app which has already been suspended by Twitter.

Although Twitter isn't advising all users to revoke third-party applications, it's always smart to keep this in check. To do so, visit Twitter's application page and click "revoke access" for each app listed. You can then go through the connection process again for the apps you still want to use.

Cleaning house like this is a good practice in general — you may be surprised about how many third-party providers you granted access to your account since signing up.

UPDATE: The story has been updated from its original version with a quote from Twitter, as well as details about how the hacker claims to target sites in the name of Islam.

Image: Mashable composite; images: Flickr, DFectuoso and iStockphoto, letoakin