SHANGHAI, March 21 -- A patient suspected of having cancer entered a hospital in Shanghai on Friday morning, injuring three medical workers and a security guard with a wood chopper, the local government said.

The attack happened at 10:40 a.m. in the Fifth People's Hospital of Shanghai, leaving one surgeon, two nurses and a security guard injured.

The attacker surnamed Zhang, 68, broke into the surgery department on the second floor and struck a surgeon surnamed Cai in the head and hands with the chopper.

While Cai struggled to get out of his office, the attacker followed and attacked two nurses and a security guard on his way out.

Zhang was immediately caught by police.

With injuries to his right hand, the surgeon may no longer be able to perform operations, Xiang Ming, deputy president of the hospital, told Xinhua.

The medical workers suffered head injuries but their situations were not life-threatening.

Xiang said the attacker had been admitted to the hospital twice in February with swollen ankles.

"While hospitalized, he refused to cooperate with our doctors and asked to be discharged. When he came back again, a biopsy showed possible cancer. He was found trying to jump out from his sickroom," said Xiang. "We are shocked. While in hospital, he never complained."

Xiang said the attacker refused therapy and left the hospital without signing discharge papers on Feb. 16.

In a statement, the Shanghai Municipal Government urged local health and police departments to take effective measures to protect the lives of medical workers.