A month-long campaign has been launched against websites that "spread pornography and threaten the morals of young people", the government said Monday.
The campaign, whose targets include Google and Baidu, is being run by the Ministry of Public Security and six other central agencies, a statement posted on the government's website said.
Cai Mingzhao, deputy director of the Information Office of the State Council, said in the statement: "These websites violate public morality and harm the physical and mental health of young people."
Huang Chengqing, deputy secretary-general of the Internet Society of China, said: "Pornography is banned in China and websites that feature erotic content are morally offensive."
Google and Baidu, the most popular search engines in China, failed to take "efficient" measures after receiving notices from the Internet watchdog that they were providing links to pornographic material, the statement said.
Web portals Sina and Sohu, and a number of video sharing sites and bulletin boards were also said to have "problematic photos, blogs and postings".
Cui Jin, a public relations official for Google China said "finger pointing should differentiate between the producers and non-producers of pornographic materials".
"Google does not produce nor own any content or websites," she said.
The firm has always abided by local laws and will delete links to sites if we are told they contain illegal content, she said.
"We have also adopted 'safe search' as the default setting, which automatically blocks sites with such content," she said.