BEIJING - Most youth crime in China can be blamed on negative influences from violent or pornographic Web sites, a police spokesman said on Thursday, justifying the country's latest crackdown on the Internet.

"In recent years from the cases we have discovered, the proportion of young people guilty of cheating, rape or robbery who are given to using the Internet or have been corrupted by online filth, is very high," spokesman Wu Heping said.

"Our preliminary figures for arrested youth criminals is that almost 80 percent of them have been seduced by the Internet," he told a news conference.

"It makes people very pained to know that crimes are committed by people corrupted by obscene pictures and images," Wu said.

Last week China announced a new campaign against Internet pornography that would also take aim at fraud, illegal lotteries and "rumour-spreading" to protect the country's mainly young Internet users from "negative online influences", state media said.

"The public security system will uphold the law during this campaign and also take tips from the public to clean up the pure space of the Internet," Wu added.

Last November a Chinese court sentenced the founder of the country's largest pornography Web site to life imprisonment.

Pornography was among the vices almost wiped out in China under the strict, puritanical rule of Mao Zedong. But since economic reforms began and social controls were loosened, it has become more readily available.

China has an army of cyber police who patrol the Internet for unfavourable content, but their targets are more often politically sensitive subjects than pornography or online scams.