"In dealing with the subject, take care to leave no blood on the face, no wounds on the body, and no people in the vicinity," states the manual, entitled Practices of City Administration Enforcement.

The book was reportedly designed as a training guide for the Chengguan, a type of police force that is charged with targeting anyone it feels is disrupting the peace, ridding China's cities of illegal street hawkers and unlicensed taxi cabs, and checking permits.

The Chengguan are widely reviled in China, and their heavy-handed methods frequently result in serious injuries or death. At the end of March, several thousand people in Nanchong, in Sichuan, rioted after a Chengguan officer seriously injured a student.

Three years ago in Shanghai, Chengguan officers beat Li Binghao, a 39-year-old man who intervened in a dispute, to death, according to Xinhua, the state news agency. "Officials who use violence are rarely investigated or held accountable," said the goup China Human Rights Defenders in reference to the Chengguan.

According to the Southern Metropolis Daily newspaper, an official with the Beijing municipal bureau of city administration and law enforcement confirmed that the training manual was genuine and had been used in official training sessions.

Several portions of the book were leaked onto the internet and have caused a furore. "Who put it up on the net? How did internal material come to be discussed outside?" the unnamed official asked the newspaper.

The published sections of the manual explain that officers must quell any dispute swiftly. "Without letting go of the subject, several officers shall act together and in a single move take the individual under bodily control," it said. "Each action must be effective so as not to give the subject any pause for breath."

The manual also told officers they should not consider whether they are a physical match for the subject or whether they could harm the subject. "You must become a resolute law enforcer staunchly protecting the dignity of city administrative regulations," it reportedly said.

Zhao Yang, a junior officer in Nanjing told the Southern Metropolis Daily: "These things used to be spread by word of mouth, but now they're out in the open. Things like how to protect yourself and how to hit people."

In Shanghai, hawkers said they had heard of several cases of abuse by the Chengguan, who they described as generally uneducated thugs. Chen Juan, a 28-year-old hawker who sells trinkets and hairbands, said: "They are different throughout the city. The ones near the centre of town are very violent. They do not always beat you up, but they intimidate us and usually confiscate and stomp on our goods. I was once chased down the street by a gang of them and that left me quite rattled."

However, another vendor, who asked not to be named, said it was easy to "play the game", suggesting that casual bribery took care of most problems.

"The problem is that many hawkers are doing this because they have nothing else. So when the Chengguan confiscate their goods, they put up a fight. That's why they get beaten up."