BEIJING >> China’s number of Internet users — already the world’s largest — rose to 450 million this year, more than a third of the country’s population, a senior official said Thursday.

Official statistics show that the number of users, as of the end of November, is an increase of 20.3 percent compared to last year, Wang Chen, head of China’s State Council Information Office, told a news conference. China’s population is more than 1.3 billion.

China’s boom in Internet usage has come with the growth of an equally extensive policing system, from technical filters that block sites based on certain words to human monitors who scan bulletin boards and micro-blogging posts for political dissent.

Wang said a yearlong government campaign to crack down on pornography, violence and other harmful material accessed on the Internet has resulted in the shutdown of more than 60,000 websites. In addition, government censors deleted 350 million entries of pornographic content, including text, images, and video clips, he said.

Chinese authorities investigated nearly 2,200 criminal cases, and courts handed down sentences in 1,164 cases, he said. More than 1,300 people were punished by the courts, while 58 people were given more than five years of prison time.

Wang said government censors have “made the Internet environment much cleaner than before.”

And he warned China had no intention of ending its Internet crackdown: “Our campaign has not come to a stop. This will be a long battle.”

Much of China’s online growth has come as more people access the Internet through their mobile phones using popular services that support video and other Web products. A report earlier this year by the China Internet Network Information Center said about 277 million people get online with their phones.

The Internet’s popularity poses challenges to the Communist government, which is used to exercising tight control over information. In addition to policing porn, Beijing runs an extensive system of Web monitoring and censorship to block information deemed politically subversive dubbed “the Great Firewall.”