Four people suffered minor injuries in separate grizzly bear attacks in the world-famous Yellowstone Park and nearby forests, US authorities said Friday.

The first incident occurred on Thursday when a group of four hikers came face-to-face with a young bear cub on a trail in Yellowstone.

The mother of the cub appeared almost immediately and charged the hikers.

"One person was treated at the scene, while the second injured hiker was transported by ambulance to an area hospital with bite and claw wounds," Yellowstone Park authorities said in a statement.

The confrontation lasted around one minute, with the hikers cheating death after spraying bear repellent.

Park officials said it was the first attack by a bear on humans in Yellowstone this year.

In a separate incident on Thursday, two employees of the Bureau of Land Management in Idaho were attacked while performing a forest health assessment, The Los Angeles Times reported on Friday.

One of the two men needed treatment for bite wounds on his thigh and buttocks while the second man was bitten on the hand as he attempted to use bear spray.

A spokesman for the Idaho Department of Fish and Game said the bear had probably been disturbed by the men while resting.

Yellowstone park officials advise hikers to stay at least 90 meters away from black and grizzly bears at all times.