Dating site eHarmony and music community Last.fm have warned users that their passwords may have been stolen by hackers.

The passwords were reportedly posted on the same Russian hacking web forum where up to 6.5 million passwords from professional social network LinkedIn were leaked.

"We are currently investigating the leak of some Last.fm user passwords," the UK-based music site revealed yesterday. "This follows recent password leaks on other sites, as well as information posted online. As a precautionary measure, we’re asking all our users to change their passwords immediately."

Meanwhile, eHarmony warned that "after investigating reports of compromised passwords, we have found that a small fraction of our user base has been affected".

"Please be assured that eHarmony uses robust security measures, including password hashing and data encryption, to protect our members’ personal information," the company said. "We also protect our networks with state-of-the-art firewalls, load balancers, SSL and other sophisticated security approaches."

LinkedIn users have reported receiving phishing messages asking them to update their passwords, but directing them to a counterfeit drugs website.

The company is now working with the FBI to investigate the data breach.

Users haveadvised to change their passwords for all three sites and for any other site where they use the same password.