Although the incident occurred on Monday morning, it was not reported by Shanghai media until yesterday afternoon.

A municipal government spokesman said he had nothing to add to a brief press release on the city's official news portal, eastday.com.

A spokesman at Xinhua Hospital - in the city's northeastern district of Hongkou and affiliated with the Shanghai Jiao Tong University Medical Department - also declined to comment.

According to reports, a group of between 20 and 30 mourners gathered outside the entrance to the hospital's casualty department at around 8am. They set up a funeral altar for Liu Yonghua and unfurled banners.

Press reports did not include details of Liu's death, which some outlets stated had happened yesterday morning, but did refer to a 'dispute over medical treatment' as the reason for the protest.

The hospital called the police as the mourners were 'seriously impeding' the emergency department's operations, but they were unable to persuade the family members to disperse. Sometime before 10.30am, the relatives stormed the hospital.

While a smaller party headed for the hospital's complaints department, a group of around 20 broke into the office of the director of the heart and chest surgical department on the seventh floor.

As the room was empty, they moved to the adjoining office, where they found the deputy director of the department. The doctor was stabbed twice in the chest, and the protesters attempted to throw him from a window.

Medical staff intervened, and in the ensuing scuffle, five hospital workers were stabbed and up to five others received lesser injuries.

The injuries included a 4cm stab wound in the chest of a doctor that came within 1.5cm of piercing the victim's heart, Eastday reported.

Of the six suspects rounded up in relation to the attack, four were believed to be responsible for the stabbings. One had been officially arrested by police, three were being detained and the remaining two had been placed under warning.