Google said Monday that more than 30 million people are using Google Apps, as the company unveiled enhanced security features for the Web-based suite of office tools.

"As of today, more than three million businesses have gone Google, and over 30 million users within businesses, schools and organizations now depend on our messaging and collaboration tools," Google said in a blog post.

Google Apps include products or services such as Gmail, Google Calendar and Google Docs and are seen as the Mountain View, California company's challenge to Microsoft's popular Office software.

Google said it was enhancing the security of Google Apps, which are hosted on the Web instead of on a user's personal computer and accessed through a browser, with a new secure sign-in capability called "two-step verification."

With two-step verification, a user enters a password and a verification code is then sent to their mobile device.

"This makes it much more likely that you're the only one accessing your data: even if someone has stolen your password, they'll need more than that to access your account," Google said.