Chinese state media say the heads of China's largest Internet and technology companies have agreed to help the Communist government stop the “spread of harmful information” on the web.

The official Xinhua news agency says the agreement came Saturday at the end of a three-day government workshop in Beijing attended by the corporate leaders of e-commerce giant Alibaba, search engine Baidu and online portal Sina.

Xinhua says the technology companies agreed to ensure the spread of “positive” Internet content and to “resolutely curb” online rumors, pornography, fraud and other information deemed “harmful” to the state.

China's State Internet Information Office hosted the workshop. It is one of the Chinese government's Internet regulators.

Xinhua says Chinese information technology minister Miao Wei told the seminar that Internet companies also must increase their investment in “tracking surveillance.”

China's Communist rulers have become increasingly concerned about a boom in social media websites and blogs that enable users to express their opinions and frustrations about society. Such websites sometimes avoid state monitoring and censorship. Chinese leaders vowed to strengthen their control of the Internet at a meeting last month.