BEIJING—China's population of Internet users rose 10 percent last year to 564 million even as communist authorities tightened controls on content, according to data released Tuesday.

Driven by a surge in mobile Web surfing, the country added 51 million new Internet users, a number bigger than the population of Spain, the China Internet Network Information Center reported. It said the number of Chinese Web surfers who go online from mobile phones, tablet computers and other wireless rose 18.1 percent last year to 420 million.

Chinese leaders encourage Internet use for business and education but try to block access to material considered subversive or obscene and are tightening controls.

A law enacted last month requires users to register their names following online complaints about official abuses that rattled communist leaders.

In April, China's most popular microblog services shut down for three days while operators deleted postings considered to have violated censorship rules.

That came as the country's most severe political crisis in years swirled around the downfall of a senior party figure, Bo Xilai. Authorities closed a dozen websites and detained six people for circulating rumors of a coup.

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China Internet Network Information Center (in Chinese): www.cnnic.org.cn