Chinese Internet celebrities have been told to "promote virtues" by a leading official, state media said Sunday, after a singer sparked a free speech debate by venting about bombing government offices.

Beijing expects celebrities to "uphold law", state news agency Xinhua reported the official as saying, after singer Wu Hongfei was released earlier this month following her detention by authorities over her online comments.

She said she wanted to target Beijing's housing authority and a neighbourhood committee, soon after a man set off a homemade device at the capital's airport, citing grievances with local government.

"The government expects (Internet celebrities) to uphold law and order and to promote virtues and trust," Xinhua quoted Lu Wei, director of the State Internet Information Office, as saying in indirect speech.

"They shall set an example of protecting the legal rights of citizens and denouncing any activities that harm the reputation and interests of other people," he was reported as saying in a statement after a high-level meeting on Saturday.

AFP could not find the statement on the website of the department, who could not be reached for comment Sunday.

There are more than 1.2 billion accounts on the country's popular Internet blogging websites, Xinhua said.

On two of the most popular Internet sites, the Twitter-like Sina Weibo and t.qq.com, 3,300 accounts have more than one million followers while about 200 have more than 10 million, the news agency added.

Media reported that Wu was held on suspicion of "fabricating fake terrorism information", an offence that carries a maximum of five years in jail.

In an informal online poll run by state broadcaster CCTV, 80 percent of voters did not think Wu's words constituted a crime.

Wu's comments were made just one day after a man in a wheelchair detonated a small handmade explosive device at Beijing airport in protest over historical grievances with the authorities.

The airport bomber, Ji Zhongxing, was a former motorcycle driver who despaired at his failure to win redress for what he called a 2005 police beating in southern Dongguan city that left him paralysed, though authorities there said his claims lacked evidence.

The blast destroyed Ji's hand and injured an officer, but his story triggered widespread sympathy and an outpouring of resentment at abuse by local authorities.

He has been formally arrested and could face three to 10 years in jail, his lawyer told AFP.