The number of blog sites in China reached 34 million last month, a 30 fold increase from four years ago, state media said on Tuesday, despite a series of curbs on media and dissent.

China has more than 17 million people writing blogs (short for Web logs) and more than 75 million people reading them, Xinhua news agency said.

Authors of personal blogs choose their own subject and can instantly forward their writings to friends anywhere in China or the world.

The rapid growth of blog sites in China also brought potential business opportunities to the advertising industry, Xinhua said. Some blogs written by famous people attract millions of daily readers.

The report said that out of the 34 million blog sites, 70 percent were dormant, having remained unchanged for more than a month.

The Chinese government, obsessed with maintaining Communist Party rule, routinely monitors online chat forums and bulletin boards for controversial political comment, censoring words such as freedom and democracy.

In the past couple of years, several Internet sites that were forums for candid opinion have been closed.