The pilot was killed immediately after rebels rounded up those on board after the helicopter landed in a field in the Alama district in Central Papua, said Bayu Suseno, a spokesperson for the joint Indonesian police-military operations in Papua, citing a witness.

The motive for the killing was not immediately clear. It comes nearly 18 months after the abduction by separatists of another pilot from New Zealand, Phillip Mehrtens, who remains in captivity.

A spokesperson for New Zealand's foreign ministry said it was aware of the report and that its embassy in Jakarta was seeking information from authorities, declining to comment further.

The rebel West Papua National Liberation Army (TPNPB) said it had not received a report of the incident referred to by police and could not immediately confirm the killing of the pilot on Monday.

A low-level battle for independence from Indonesia has long raged in the resource-rich western half of Papua, where attacks by independence fighters have grown deadlier and more frequent as they have procured better weaponry.

Spokesperson Bayu said the group responsible for Monday's incident was the same group currently holding Mehrtens.

The New Zealand government has repeatedly called for the immediate release of captured pilot Mehrtens, who was kidnapped on Feb. 7 last year after he landed a small commercial plane in the remote, mountainous area of Nduga.

The rebels have previously released videos of Mehrtens seeking international mediation in talks between the rebels and Indonesian authorities, one with him surrounded by Papuan fighters.

TPNPB spokesperson Sebby Sambom said on Saturday the group had agreed to free Mehrtens, but Indonesian security spokesperson Bayu on Monday cast doubt on that, describing it as "mere propaganda". Sebby did not immediately respond to a request for comment on that.