Papua New Guinea radio reports that Bougainville secessionist leader Francis Ona has died.
Bougainville's new president, Joseph Kabui, has expressed sadness at Ona's death, believed to be caused by malaria.
PNG's Bougainville Affairs Minister Sir Peter Barter also expressed sadness, saying in a statement his greatest wish was for Ona to play a real part in Bougainville's peace process.
Sir Peter and Mr Kabui had both urged Ona to join the peace process and support the autonomous government elections.
Ona emerged from 16 years of seclusion in his mountain retreat at Panguna in the lead-up to the election to proclaim Bougainville already independent from PNG.
But he did not promote outright disruption of the election.
In 1989 Ona was instrumental in launching Bougainville's long secessionist conflict which dragged on through the 1990s and cost the lives of more than 10,000 people.