A grizzly bear attacked and killed a person camping in the US.

The attack earlier today has triggered an intensive search for the bear by wildlife officials and law enforcement officers who planned to kill the animal, officials said.

The pre-dawn attack happened in Ovando, a town of fewer than 100 people, in western Montana said Greg Lemon, a spokesperson with Montana Fish Wildlife and Parks.

The bear had previously wandered into the area where the victim was camping and left but later returned, Powell County Sheriff Gavin Roselles said.

“There was an earlier contact with the bear prior to the event,” Mr Roselles said. “The bear basically came back into the campsite. It wandered into a campsite a couple different times.”

A team of law enforcement and wildlife specialists was brought in to track down and kill the bear, officials said.

A crew aboard a helicopter was assisting as searchers looked for a "daybed" where the animal might be sleeping to get out of the heat, said Mr Lemon, adding that the bear was believed to have left Ovando after the mauling.

He said his understanding is that the victim was part of a group on a bike trip.

The victim's identity was not immediately released and further circumstances surrounding the attack are under investigation.

“Our first concern is the community's well-being. The next step is to find the bear," Mr Lemon said.

Other people were camping in the vacinity of the attack.

A video camera from an Ovando business caught footage of a grizzly bear on Monday night, wildlife officials said. A bear also raided a chicken coop prior to the attack at the campsite.

Ovando saloon owner Tiffanie Zavarelli said it was the first fatal bear mauling that she knew of in the community.

Local residents are accustomed to living in proximity to bears and know the risks, but the attack has left them rattled, she said.

“Everybody's pretty shaken up right now. The population here is 75 — everybody knows everybody.

“The people from Montana, we know how to be ‘bear aware.' But anything can happen,” she added.

Grizzly bears have run into increasing conflict with humans in the Northern Rockies over the past decade as the federally protected animals expanded into new areas and the number of people living and visiting the region grew. That has spurred calls from elected officials in Montana and neighboring Wyoming and Idaho to lift protections so the animals could be hunted.

In April, a backcountry guide was killed by a grizzly bear while fishing along the Yellowstone National Park border in southwestern Montana.

The 420-pound bear in that attack was shot and killed when it charged wildlife officials as they approached the site of the mauling.

Ovando is on the southern edge of a huge expanse of wilderness that stretches to the border of Canada and is home to an estimated 1,000 bears.

In 2016, an off-duty US Forest Service law enforcement officer was fatally mauled in the region after he collided with a grizzly while mountain biking in the Flathead National Forest.

Grizzly bears involved in attacks on humans can be trapped and killed if they are considered a continued public safety threat. Bears involved in non-fatal attacks are often spared in the case of a surprise encounter or if they are protecting their young.

ed as a threatened species i n the contiguous U.S. since 1975, allowing a slow recovery in a handful of areas.