Officials in western Japan's Osaka City say a whale that strayed into a bay there has died.

The 8-meter-long whale was first spotted on Monday in shallow waters near the mouth of the Yodo River.

The local Coast Guard had been monitoring the mammal, thought to be a sperm whale.

Although the whale was initially seen spouting water, it later became less active. Patrollers found it immobile on Friday morning, about 400 meters from a nearby pier.

City officials and experts from an aquarium went out to the whale in a rubber boat and confirmed it was dead.

The rare sighting of a whale had drawn crowds to Osaka Bay.

The city says when a whale carcass is found, local authorities are responsible for disposing of it. Officials plan to consult experts to decide what to do about it.