The number of internet users in China grew by 15% during the past six months to 68 million, the government has said.

China has the world's second-biggest online population, but is far behind the United States, which has more than 165 million people online.

In China, users are mostly young, male and single, according to the survey conducted twice a year by the China Internet Network Information Centre.

China promotes internet use for business and education, although the communist government censors chat rooms and tries to block access to foreign sites run by dissidents, human rights groups and news organisations.

The biggest single group online in China is people aged 18 to 24, making up 39% of the total, the agency said. It said 40% of users are women.

Chinese web users spend an average of 13 hours online each week, 10 hours of which is spent playing games, the agency said.

The number of websites in China grew to 474,000, a rise of 28%, with 250,000 registered using its ".cn" domain-name suffix.

The Chinese internet agency's survey is the most widely watched set of figures on China's online use, although results can differ widely from surveys carried out by commercial and academic researchers.