The Indian subsidiary of online deals giant Groupon has accidentally published email addresses and passwords from its subscriber database, the company and reports said Wednesday.

Groupon said in a statement sent to AFP that it "was alerted to a security issue" affecting its Sosasta.com subsidiary last Friday and that it "corrected the problem immediately."

Sosasta, an online discount portal acquired in January 2011, informed its subscribers Tuesday and posted a message on its Facebook page asking users to "change your Sosasta password immediately."

Daniel Grzelak, founder of the Internet security website shouldichangemypassword.com, found the security breach while running a Google search for publicly available databases of email addresses and passwords.

"A few hours and tweaks later, this database came up," he told the Internet security site risky.biz, which said SoSasta's database contained information on 300,000 people.

"I started scrolling, and scrolling, and I couldn't get to the bottom of the file. Then I realised how big it actually was."

Grzelak's website holds a database of 1.3 million compromised email addresses, allowing users to check if their own email address is among those deemed unsafe.

"There are thousands of these databases indexed by Google," he told risky.biz. "This just happened to be by far the biggest I found."

Groupon said it would review Sosasta's security procedures thoroughly and put in place "measures designed to prevent this kind of issue from recurring."

"Groupon takes security and privacy very seriously. Our users' trust is of paramount importance to us and we deeply regret this incident," the firm said. "This issue does not affect data from any other country or region."

Groupon, based in Chicago, announced plans to go public earlier this month, after turning down a $6 billion takeover offer from Google last year. It currently has 83.1 million subscribers and operates in 43 countries.

The company operates on the principle of collective buying, negotiating with businesses to offer discounted purchases which come into effect when a minimum number of subscribers agree to pay for the same deal.