More than 900 improper smartphone applications provided by Baidu Inc, China's largest search engine, have been cleaned up, the company said on Thursday.

To purify the cyberspace, especially the mobile network, Baidu has taken a lead to remove 903 problematic applications, including the ones with pornographic information, from its app store.

On Nov 27, more than 50 companies in Beijing, including Baidu, signed an agreement to improve their self-discipline in developing applications, under a requirement of the capital's cyberspace administration.

The enterprises promised to eliminate illegal ones by themselves if they find and verify, hoping to clean the online environment from root, according to the agreement.

In 2014, more than 2,200 websites and more than 20 million of micro blogs, online forums and Wechats with improper moves, such as broadcasting pornographic information, were shut down, the administration said.

One billion pieces of illegal messages on the Internet were cleaned out over the past year, it added.

Also since 2014, a few Chinese network giants, including Baidu, Tencent and Sina, developed campaigns against online rumors and unhealthy information on their products, services or app stores.

The administration said such the crackdown will be continued this year, and more Internet companies are asked to join the team.