WASHINGTON - April 26 - Amnesty International today demanded the immediate investigation into the killing of a prominent Cambodian environment activist, after the activist and a military police officer were shot dead on Thursday in Cambodia's south-western Koh Kong province.

Chut Wutty was an outspoken critic of illegal logging and director of the Natural Resource Protection Group (NRPG), a Cambodian NGO that campaigns against the destruction of the country's forests. He had received threats because of his activities.

"This shocking incident undoubtedly rings alarm bells for all activists who have worked with Wutty," said Rupert Abbott, Amnesty International's researcher on Cambodia. "There must be accountability in this case, with an immediate and proper investigation into what happened."

Other military personnel were apparently present during the shootings, but the details of the incident remain cloudy.

Two women journalists from the Cambodia Daily newspaper -- Cambodian Phorn Bopha and Olesia Plokhii, a Canadian national -- were with Wutty when he was shot. Both were initially detained, but have since been released.

"The Cambodian authorities must guarantee the safety of the two journalists caught up in this tragedy," said Abbott. "As the only individuals who may know what happened, they could be at risk."

Amnesty International is a Nobel Peace Prize-winning grassroots activist organization with more than 3 million supporters, activists and volunteers in more than 150 countries campaigning for human rights worldwide. The organization investigates and exposes abuses, educates and mobilizes the public, and works to protect people wherever justice, freedom, truth and dignity are denied.