Four people at a renowned Shanghai hospital were wounded by a knife-wielding assailant on Saturday, Reuters reported.

Officers raced to the more than 100-year-old Ruijin Hospital on Saturday morning after receiving calls about an attack, police said.

Videos on social media showed chaos as visitors clambered under turnstiles to get out of the hospital while doctors were seen running out with their patients, some in wheelchairs and one on a mobile bed.

A long trail of blood was seen on the marble surface of a flight of stairs in one video.

At the Shanghai hospital, police found a man holding a crowd hostage with a knife on the seventh floor of the outpatient department. When the man threatened to hurt the hostages, the police opened fire, subduing him, according to local police.

None of the wounded is in a life-threatening situation, and the incident is being investigated, the police said.