BEIJING (AFP) - A Chinese singer who was detained for threatening to bomb government offices after a man detonated a device at Beijing airport has triggered a debate about free speech.

The airport attacker Ji Zhongxing - a wheelchair-bound former driver who said he had failed for years to win redress after a police beating left him paralysed - garnered some sympathy after the explosion destroyed his hand and injured an officer earlier this month.

Hours later, rock singer Wu Hongfei said on Sina Weibo, a social network service akin to Twitter, that she wanted to blow up the housing authority and a neighbourhood committee in the capital.

She was detained days later on suspicion of "fabricating fake terrorism information", a crime which carries a maximum sentence of five years, the China Daily said.

In an informal Sina Weibo poll by the state broadcaster CCTV, more than 81 per cent of 31,000 people who had responded as of Monday felt her comments did not constitute a crime.

Her lawyer Li Jinxing argued that her words did not pose a credible threat and were spoken in anger.

"Most people would see this as venting and not think she would really go and bomb these places," the Beijing Times quoted him as saying.

Detaining her for an "inappropriate Weibo comment has huge significance for defining freedom of speech versus illegal behaviour on the Internet", he added.

Police detained two other men for also allegedly threatening to set off bombs in public places around the capital, it added.