Indonesian police said on Wednesday that a pilot and co-pilot of a small commercial plane died after unknown assailants opened fire on the aircraft when it landed in the country’s easternmost region of Papua.

Axar.az informs, citing Reuters, the Smart Air plane, which was carrying 13 passengers as well as the pilots, landed at Korowai airport in Boven Digoel, South Papua province, on Wednesday at 11.17 a.m. local time (0217 GMT).

When the shooting began, the pilots and passengers left the plane and headed to a forested area near the airport, he said.

The pilot and co-pilot were killed, but all passengers were safe.

Cahyo said it was unclear who carried out the attack on the Cessna Caravan plane, after he was asked about the possible involvement of Papuan rebel groups.

A low-level but increasingly deadly battle for independence has simmered between security forces and rebels in resource-rich Papua ever since it was controversially brought under Indonesian control in a vote overseen by the United Nations in 1969.