Four passengers who suffered injuries in an arson attack on a bus on July 5 in Hangzhou were discharged from hospital on Thursday.

The attack, allegedly committed by Bao Laixu, 34, injured 30 passengers, 22 seriously. The four passengers discharged are the first to be released from hospital.

The remaining 18, including three children, remain in hospital, and one is on a respirator.

Han Chunmao, chairperson of the Department of Burns at the Second Affiliated Hospital of Zhejiang University's School of Medicine, said that all patients were responding well and have emerged from the shock phase, the most dangerous phase for burns patients.

"A total of 52 operations have been carried out. It is a miracle that some patients with 90 percent burns not only survived but also are recovering rapidly," he said.

The arson suspect is among the most seriously injured.

Han said the remaining patients are on course to be discharged soon and will then receive rehabilitation in Hangzhou.