BEIJING - Major web portals and telecom operators have signed a letter of commitment vowing to end the spread of the online pornography.

Web portals including Sina, Baidu, Tencent and the official websites of Xinhua News Agency and the People's Daily, the flagship newspaper of the Communist Party of China, and the three telecom giants China Mobile, China Unicom and China Telecom, jointly signed up, on Monday.

The signing ceremony was organized by the National Office Against Pornographic and Illegal Publications and the China National Committee for the Wellbeing of the Youth.

The joint signing is aimed to intensify the crackdown on online pornography and create a healthy cyberspace for youngsters during the summer holidays. Students tend to use the Internet frequently during the long break, according to the office's deputy director Mao Xiaomao.

In the commitment letter, web portals and telecom giants will strengthen blocking porn information spreading through blogs, microblogs and instant communication tools like QQ or Fetion. They will also intensify monitoring and eradicating vulgar, gang-related and porn content in online literature and songs.

Mao encouraged the public to report violators through the office's website (www.shdf.gov.cn) or by dialing the hotline number 12390.

Web portals and telecom operators promised not to carry or spread any porn and "unhealthy" contents. They will be asked to delete the contents and apologize publicly if they are found "breaking the promise."

No material punishments were listed in the commitment letter.

But Sina's Weibo.com and Tencent's t.qq.com, two major microblogging sites in China, suspended their comment functions from March 31 to April 3 to check for false information posted on their sites.

Later, chiefs of Sina, Baidu and Tencent all said they will co-operate with relevant government departments to banish online rumors.