Video footage of a man being brutally attacked with a steel lock during anti-Japanese protests, uploaded to the Internet on Wednesday, has enraged the public and put pressure on police to step up their hunt for the attacker for a 12th day.

Attacked by anti-Japanese protestors, a severely injured Li Jianli lies in front of his Toyota with his wife at his side in downtown Xi’an, Shaanxi province, on Sept 15. [Photo/China Daily]

Police have made public pictures of more than 40 wanted men after violent protests broke out in more than 80 cities across China after the Japanese government's decision to "nationalize" the Diaoyu Islands on Sept 11. At least 10 suspects have turned themselves in.

The new footage of the attack in Xi'an, capital of Shaanxi province, begins with 51-year-old Li Jianli standing beside his Toyota car surrounded by an angry crowd on Sept 15. There is a shout of "Don't hurt him", and then a man in a white T-shirt lunges at Li, striking him on the head with a U-shaped steel bicycle lock. Li falls to the ground where his attacker hit him a further three times with the lock.

Li is then seen leaning motionless against the side of a car as a woman who appears to be his wife kneels beside him and screams, "He is dead!"

A man in the crowd then says, "You attack Chinese? Are you Japanese?" This is followed by a shout of, "Someone save him!"

Following the attack, a doctor performed brain surgery on Li, whose skull was fractured. He remained in intensive care for three days after the incident.

Chang Shulin, deputy director of the hospital's neurosurgery department, on Thursday said Li had suffered a heavy open cranio-cerebral injury and would need a long time to recover. He is conscious but unable to speak or move, he added, and will undergo another operation in six months to repair his damaged skull.

Bai Yansong, a commentator with China Central Television, described violence during the protests as being conducted "in the disguise of patriotism".

"People cannot strive for a just objective through illegal means," he said.

Lianhu district police office in Xi'an posted four pictures of Li's attacker on its micro blog on Sept 22, asking for anyone with information to come forward.

A police officer surnamed Luo, who is in charge of the case, said dozens of police are working day and night on the case, and they have received useful information from the public.