China has launched a campaign to enforce curfews at Internet cafes before schools let students out on summer vacation, a news report said Monday.

The focus of the weeklong crackdown, launched Saturday, "is to prevent the entry of kids under the age of 18," said a Culture Ministry official quoted by the China Daily newspaper.

It said violators could face penalties ranging from being shut down for 15 days to losing their license to operate.

China has the world's second-biggest population of Internet users after the United States, with 110 million people online, but tries to regulate what Web surfers can see online.

Rules on children in Internet cafes were imposed after Chinese officials warned that students were spending too much time playing online games and were getting access to violent and obscene material.