Major Chinese websites have vowed not to attempt to exploit pornographic content to boost their click rates, amid a national crackdown on online pornography.

The websites, including 15 affiliated to state news organizations, and six commercial websites such as sina.com, qq.com and baidu.com pledged support for the crackdown at a conference held by the State Internet Information Office (SIIO) on Monday.

Ren Xianliang, deputy director of the SIIO, urged the sites to rid themselves of any porn and constantly review their content.

The SIIO will step up supervision over websites, according to Ren.

China has shut down 110 websites and some 3,300 accounts on China-based social networking services, such as WeChat and Sina Weibo, as well as deleting online forums in the recently launched "Cleaning the Web 2014" campaign, the SIIO said on Sunday.