Chinese officials say the number of Internet users in China has risen to more than half a billion.

The China Internet Network Information Center said Monday China’s Internet population rose to 513 million by the end of 2011, a 12 percent increase over 2010. It said the number of people surfing the web on mobile telephones rose 17.5 percent to 356 million.

Almost half of China’s online population uses near-instant service microblogs, known as weibos in China. Weibos are similar to Twitter, the most popular microblogging platform in the world, which China bans.

Weibos are a huge challenge to government attempts to control information in the populous country. The Chinese government blocks web content it believes is politically sensitive. The Communist Party is concerned about the power of the Internet to influence public opinion.

In an effort to exert more control over weibos, some city governments are now requiring Internet users to register under their real names, making it easier for authorities to track them.