The fixed-wing aircraft was approaching an airport in the port town of Kiunga in the country's west on Wednesday when it crashed into a shallow swamp, Western Provincial Police Commander Joseph Puri said in a statement. Air crash investigators were trying to determine what caused the accident, Puri said.
A helicopter pilot from a local drilling company spotted the crash and transported three survivors to the Kiunga hospital, but all three were declared dead on arrival, Puri said.
One Australian man was among those killed on board the Sunbird Aviation aircraft, Australia's Department of Foreign Affairs and Trade said, declining to provide further details.
The Pacific island nation has a patchy record of flight safety, given its mountainous terrain and frequently extreme weather conditions. One of the worst accidents in recent years happened in 2011, when a plane crashed during stormy weather in a remote forest on the country's north coast, killing 28 of the 32 people on board.
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