Twitter Inc said on Tuesday that email addresses and phone numbers uploaded by users to meet its security requirements may have been 'inadvertently' used for advertising purposes.

The micro-blogging site said the issue was rectified as of 17 September.

"We recently discovered that when you provided an email address or phone number for safety or security purposes (for example, two-factor authentication) this data may have inadvertently been used for advertising purposes, specifically in our Tailored Audiences and Partner Audiences advertising system," Twitter wrote in a blog post.

"This was an error and we apologize," the company said.

Image: Reuters

Twitter did not disclose how many people were affected by this.

"We cannot say with certainty how many people were impacted by this, but in an effort to be transparent, we wanted to make everyone aware. No personal data was ever shared externally with our partners or any other third parties. As of September 17, we have addressed the issue that allowed this to occur and are no longer using phone numbers or email addresses collected for safety or security purposes for advertising."

Social media companies, including Twitter and Facebook, have faced heat from users and regulators globally on how their platforms handle user data.

Twitter said when advertisers uploaded their marketing lists, it may have matched people on Twitter to their list based on the email or phone number the Twitter account holder provided.

With inputs from Reuters.