U.S. officials have confirmed that a female grizzly bear has killed a man out hiking with his wife at Yellowstone National Park.

According to reports the couple apparently surprised the bear who was with its cubs in an isolated area near the middle of the park.

A spokesman for the park, Al Nash, said that the man and his wife had seen the grizzly bear earlier on the Wednesday but had decided to continue with their hiking:

“The second time they saw it, the bear was coming towards them.

“The husband reportedly told his wife to run and she did so.

“That is when the bear attacked and killed the man”, said Mr Nash.

Officials further revealed that the woman did not witness her husband’s fatal attack, and had driopped to the ground when the grizzly bear chased after her.

The bear lifted her off the ground by her rucksack before dropping her and running off, leaving her bruised but not seriously wounded.

When another group of hikers heard the woman’s screams for help they called 911 for the rangers to assist.

Despite this being Yellowstone’s first fatal bear attack since 1986, and the area has been closed with warning signs in place Mr Nash added:

“This was probably a defensive attack on the part of the bear.

“The bear felt threatened and attacked the person.

“If that is the case we do not have plans to track or dart the bear.

“This is an extremely rare incident.

“Simply seeing a bear in the distance does not necessarily require you to run away.

“You just need to be careful and mindful and stick to designated trails, walk in numbers, make lots of noise and carry a bear pepper spray.”

Yellowstone National Park is home to several hundred grizzly bears which can weigh up to 600lb (270kg) and these giant animals are one of the parks biggest tourist attractions.