Following the deaths of three brown bears within a few hours, the Greek environmental organization Kallisto has called for a thorough investigation into the incidents.
The organization said in a statement issued on Monday that two animals had been shot dead and another killed by poisoned bait.
The incidents over the weekend highlighted the ongoing threats to the protected species in Greece, Kallisto said.
Killing or injuring a bear is a criminal offence and violates both Greek and international conservation regulations.
The organization called on the authorities to bring those responsible to justice. Encounters between bears and humans should not be used as a pretext for vigilante justice.
Instead, the relevant authorities must be informed so that the prescribed response and protection measures can take effect.
However, some residents in north-western Greece are afraid, as bears are now venturing into populated areas as far as the town of Kastoria, searching for food.
Drawn by household waste and orchards, the animals are increasingly coming into contact with humans, with some being killed by individuals as a result.
