A villager in rural east China unhappy over social injustice detonated an explosive in a local government building Monday, killing himself and wounding six others, state press said.

Qu Huaqiang, a "disgruntled petitioner," allegedly set off homemade explosives at the government offices in Tengjia township, Shandong province on Monday morning, Xinhua news agency said.

It was not clear if the injured were government officials. No other details were immediately available.

News of the bombing circulated widely on the Internet with numerous microbloggers expressing sympathy with the suspect bomber, while criticising as a sham China's petition system, an age old institution aimed at addressing injustice.

An official in Tengjia when contacted by AFP confirmed the bombing, but denied that Qu was a petitioner. Township authorities were investigating the incident, he said, while refusing to comment further.

Over 30 years of robust economic growth has produced a yawning income gap between China's rich and poor, with the nation's poorest often complaining of exploitation by local government over cheap labour and inexpensive farmland.

Petitioning the government over alleged injustices has long been seen as a sole way to seek redress, but is rarely, if ever, successful, they say.

The system has largely failed to accommodate the enormous amounts of petitions received, while police often resort to placing petitioners in extra legal jails to control their activities, rights groups have said.

After the news of the bombing spread, microbloggers also appeared to support such conclusions.

"This proves once again the so-called People First petition system is a sham. It misleads the people and induces violence," said Yu Jianrong on Sina Weibo, a popular microblog.

"The so-called legal petition system is becoming a trap for petitioners. I propose the repeal of the petition system," said Shijie gongmin_Daweiwangsai.

Said Nizhigala, "This is a good comrade who knows revolt. I pay my respect to him."

In apparent concern over copycat bombings, Xinhua later retracted its characterisation of Qu as a "disgruntled petitioner" from its Chinese language news report.