CANBERRA, May 22 (Xinhua) -- Three men are in a serious condition after a helicopter crashed in Australia's iconic Kakadu National Park.

The helicopter had two national park staff and a private contractor on board when it crashed in the southern part of the Northern Territory (NT) park during an animal control muster on Tuesday.

One of the injured men was able to free himself from the wreckage and call for help despite his injuries, aeromedical service CareFlight confirmed in a statement.

"The first patient was freed and winched into the helicopter before being flown to meet a CareFlight King Air at Cooinda Lodge for transport to Royal Darwin Hospital," it said.

"A CareFlight flight nurse and doctor continued to care for the 59-year-old man during the transfer to RDH.

"He arrived in a serious condition with significant injuries.

"The other two patients were treated at the scene, before being winched into the helicopter and flown directly to Royal Darwin Hospital and arrived just after 6pm.

"Both patients, in their 50s, were in a serious condition."

News Corp Australia reported on Tuesday night that one of the injured men was Fred Hunter, one of Kakadu's most esteemed rangers.

In a post on social media, Hunter's brother-in-law said that injuries sustained included broken bones.

The Australian Transport Safety Bureau (ATSB) confirmed it was aware of the crash but was "gathering further information" before deciding whether to launch an investigation.

Kakadu is one of the Australia's top tourist attractions, with 200,577 people visiting the park in 2018.