The number of Internet users in China rose last year by nearly 56 million to more than half a billion, nearly half of whom used weibos, or microblogs, according to latest official figures. China\'s online population -- the world\'s largest -- hit 513 million in 2011, a 12.2 percent increase on the previous year, the China Internet Network Information Center (CNNIC) said in a statement on Monday. Of these, 48.7 percent -- or nearly 250 million people -- now used weibos, compared to just 63.1 million at the end of 2010, posing a huge challenge to government attempts to control information in the country of 1.3 billion. The weibos -- hugely popular microblogging services similar to Twitter, which China bans -- have become the most popular medium for web users to vent their anger over corruption, scandals and disasters, or alert others about protests or riots. The number of people using more traditional communication tools such as emails, web forums or blogs was falling, the CNNIC said. The government blocks web content it deems politically sensitive in a vast censorship system dubbed the \"Great Firewall of China\", and is hugely concerned about the power of the Internet to influence public opinion. In a bid to exert more control over weibos, some cities such as Shanghai and Beijing now require users to register under their real names, making it easier for authorities to track them. CNNIC said the number of people in rural areas using the Internet also rose last year -- up 8.9 percent to 136 million in 2011 -- but huge disparities still exist between rich and poor regions. While more than 70 percent of Beijing\'s population used the Internet last year, only 24.2 percent of people went online in the southwestern province of Guizhou -- the poorest in China. The number of people surfing the web on mobile phones reached 356 million in 2011, up by nearly 53 million, the industry group said. It added that while the number of web users continued to rise in the world\'s most populous country, the rate of growth was gradually slowing.