A female grizzly bear attacked and fatally wounded a visitor at the Yellowstone National Park in what seems like an apparent attempt to defend her cubs on Wednesday morning, officials at the park said.

The incident occurred while the visitor and his wife traveled on the Wapiti Lake trail, located east of the Grand Loop Road south of Canyon Village.

Upon hearing the victim's wife crying for help, nearby hikers called park rangers for rescue.

It is extremely unfortunate that this couple's trip into the Yellowstone backcountry has ended in tragedy. Our heart goes out to the family and friends of the victim as they work to cope with their loss, Dan Wenk, Superintendent of Yellowstone National Park said in a statement.

This has been the first bear-attack at the Yellowstone National Park since 1986 since such attacks are extremely rare.

The incident is under investigation and all trails and backcountry campsites in the area have been closed until further notice.