Three doctors were severely injured when a man, allegedly unhappy with his treatment, set fire inside a hospital in the capital of North China's Shanxi province.

The accused Ji Ruilin, 34, first emptied a bottle of petrol inside the hospital before lighting up the fuel, leading to an explosion.

Ji, a factory owner from Qingxu county of Taiyuan, broke into an office in the Affiliated Hospital of China Institute of Radiation Protection and launched his attack, scalding three doctors, including the president of the hospital, and himself.

A doctor at the hospital, who did not wish to be named, said Ji was unhappy with the medical treatment he received for his shoulder dislocation last year.

He claimed for compensation from the hospital several times, saying he was still feeling discomfort in his shoulder, the doctor said.

The attack was the latest in a series of violent disputes between hospitals and patients that have prompted hospitals to hire security guards to protect their staff.

Ji allegedly broke into the hospital director's office at 11:50 am, just before lunch break, with a bottle of petrol and a lighter and set fire in the cabin, where director Zhang Zhiping, the hospital's Party secretary Fan Zehua and doctor Lu Chao were in discussion.

"I heard the explosion and rushed to the first floor to find a woman on fire calling out to me for help. Then I recognized her voice, my best friend's," said doctor Zheng Wen'ge, Lu's colleague and friend.

While Lu was rolling all over the grass trying to put out the fire, the attacker, who was also injured, walked out of the building smiling, Zheng said.

"I thought he was a patient and rushed over to help him when I realized he was the attacker," she said.

"He would not stop smiling. That scared me a lot," she said.

The fire was put out soon, but not before Lu, Zhang and Fan suffered extensive burns. All of them have been admitted to the ICU of the provincial burns treatment center.

Lu suffered 98 percent burns. "It's hard to say whether she will survive," said Kang Ailing, the chief nurse of the ICU.

Zhang and Fan are out of danger now, Kang said.

The accused is receiving treatment at another hospital secured by the local police, who could not be reached for comment on Tuesday.

Doctor Zheng said she was feeling very angry. "How can a person do such a thing? It's meaningless, but brought a lot of sufferings to the victims."

Lu, 29, got married last year and does not have a child yet, she said.