"The six tourists have admitted drowning the bear after it attacked them. They claim they did it to protect themselves," Filip Zieba, a ranger from the Tatra Mountains national park, told AFP.

However, a two-year-old bear weighing 46 kilos (102 pounds) is no real threat to humans and the animal must have been provoked, Zieba said.

Rangers found bread at the scene, suggesting that the Polish tourists had fed the bear with their picnic sandwiches, which is banned, Zieba said.

The tourists came across the bear Saturday in the Chocholow Valley as they returned from a mountain hike.

Two of them subsequently went to a hospital in the resort town of Zakopane to have treatment for the injuries purportedly caused by the animal.

Doctors, however, noted nothing but scratches and no sign of wounds that could have been caused by bear claws. They decided to alert the park rangers.

The bear's body, in contrast, showed signs of injuries that could have been caused by stone-throwing, and experts were due to carry out an autopsy to try to confirm the cause of death.

"If our suspicions are confirmed it will be something never seen before in the history of this park, and an unacceptable act of barbarity," said Zieba.

Prosecutors in Zakopane have launched an investigation and the hikers could face two years' jail.

Dozens of brown bears -- a threatened species in Europe -- roam the Tatras, which straddle Poland and Slovakia and are part of the Carpathian range.

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