Sydney stabbing leaves 1 dead, 2 hurt

Three men were treated at a Sydney hospital for stab wounds, one of whom died. File photo / Thinkstock

Three men who staggered into a Sydney hospital with stab wounds including one who later died were known to them, police say.

Liverpool Hospital's emergency department was forced into lockdown as a 24-year-old from Macquarie Fields and a 25-year-old Ingleburn man stumbled in with upper body injuries about 9.30pm on Monday.

Moments later, a Mount Pritchard man aged 30 also arrived with stab wounds. The 24-year-old died a short time later, while the other two remain in a serious but stable condition. It is believed all three men knew each other.

Police say they don't know where or how the men were injured, including whether they attacked each other.

A grey sedan has been seized by investigators, raising questions over whether they walked to the hospital or arrived by car.

Initial information led officers to Bigge Park next to the hospital but after a search of the area no crime scene has been established.

Witnesses at the hospital say the men's late-night arrival was "chaotic".

"There was one sitting directly across from my room and he was just out of control, cursing, swearing and going off at the police," one woman told the Nine Network on Tuesday.

Police are appealing for witnesses to come forward. A post mortem will be conducted on the Macquarie Fields man later on Tuesday.

- AAP