A woman hiking in the US state of Colorado has been found dead after what authorities suspect was a rare attack by a mountain lion.

The woman was found unresponsive by other hikers around noon Thursday, local time, in a secluded forest area on the Crosier Mountain trail, north-west of Denver.

Colorado Parks and Wildlife (CPW) said mountain lion attacks on humans were rare, with the last death in the state 27 years ago.

The hikers who found the woman saw a mountain lion near the woman's body and scared it away by throwing rocks. 

CPW spokesperson Kara Van Hoose told reporters a doctor was among the hikers and tried to help the woman, but found no pulse. 

Nearby trails were closed while CPW officers who went to the scene shot dead two lions in the area. 

It is not known if one or more animals were involved in the suspected attack, the agency said in a statement.

"There were signs that this was consistent with a mountain lion attack," Ms Van Hoose told a press conference.

Rafael Moreno, from the Larimer County Coroner's Office, said an autopsy had been scheduled for next week, after which the office would release the woman's identity and cause of death. 

'We do expect conflicts'

Ms Van Hoose said CPW pathologists were performing necropsies on the dead lions to check for abnormalities and neurological diseases, like rabies and avian influenza, as well as human DNA. 

She said CPW policy mandates killing any mountain lion involved in an attack on a human to prevent repeat incidents. 

If human DNA is not found on either dead lion, authorities will continue to search for animals that might have been involved. 

Colorado has a healthy mountain lion population, estimated by CPW to be between 3,800 and 4,400 adults. 

Conservation efforts have brought the species back from near extinction in the 1960s due to bounty hunting.

"Because mountain lions are really common in this area, we do expect to have conflicts [with people]," Ms Van Hoose said.

Hiker tells of fighting off mountain lion

Another hiker has told the Associated Press he fought off a mountain lion in November near where the woman was found dead.  

Gary Messina, 32, from nearby Glen Haven, Colorado, said he was running along the same trail in the dark when his headlamp caught the gleam of eyes in the brush. 

Gary Messina took a photo of the mountain lion he says attacked him.  (AP: Gary Messina)

Mr Messina said he used his phone to snap a quick photo before a mountain lion rushed him.

He threw the phone at the animal, kicked dirt and yelled as the lion kept trying to circle behind him. 

After a couple of minutes, he broke a large stick off a log, hit the lion in the head and it ran off, he said.

Mr Messina said he reported his encounter to wildlife officials.

Ms Van Hoose said signs were then put up to warn people along trails in the area, with the signs later removed. 

AP/Reuters