Gunman dead, hostages safe following siege at Aussie industrial site in Sydney

A gunman involved in a six-hour siege on the outskirts of Sydney has died from a self-inflicted gunshot wound.

Three hostages were taken to safety shortly after 5 p.m. (AEDT) and attended to by ambulance paramedics.

Heavily armed police had been at Inline National Signage in Ingleburn, located in Sydney's southwest since 10:45 a.m.(AEDT) when three people were shot, one of whom later died.

Earlier this afternoon, a person of interest was arrested and led away in handcuffs in relation to the incident, said Mark Brett, acting New South Wales (NSW) police commander.

"The deceased is 43 years old. Two men with gunshot wounds have been conveyed to Liverpool Hospital," Brett said.

"One is undergoing emergency surgery, the other has superficial wounds to the lower part of his body."

Five gunshots were heard in the area according to nearby businesses.

An employee at a nearby business told AAP that one person was dead.

"Police told us not to go near windows," the employee said.

Australians are still on alert following a lone gunman who took 17 hostages at a cafe in Sydney in December 2014.

Two hostages were killed along with the gunman during the 16-hour siege. Endit