Lieutenant Colonel Alaric Delos Santos, spokesperson of the military's Western Mindanao Command, confirmed the accident, saying it involved a Philippine Air Force search and rescue aircraft.
The military has yet to issue a full statement on the crash.
Mujiv Hataman, a lawmaker from Basilan province, said the helicopter crashed around 1 p.m. local time somewhere in Upper Manggas, a remote village in the coastal Lantawan town on the island province.
Authorities said bad weather may have caused the aircraft to crash. There was a strong gust of wind followed by a heavy downpour before the incident occurred.
Initial media reports said the helicopter, carrying four people, was bound for Zamboanga City from Jolo town in southern Sulu province to evacuate civilian personnel when it crashed.
The bodies of the four onboard were recovered from the crash site.
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