The president of the autonomous Papua New Guinea province of Bougainville, Joseph Kabui, says the sudden death of the longtime provincial administrator, Peter Tsiamalili, is a devastating blow.
The 54 year died at the weekend in his sleep.
Mr Kabui says Mr Tsiamalili had had two recent positive medical checkups so a post mortem is to be conducted in Port Moresby.
He says Mr Tsiamalili's death is a tragic loss because all the reconciliation and redevelopment on Bougainville revolved around him.
Mr Kabui says his greatest achievement was to help translate the Bougainville peace agreement into reality.
"Late Peter, with all his wealth of experience and exposure both nationally and internationally, was the most appropriate person to be able to help us, the politicians, to bring into being, here on the ground, here on Bougainville, the whole ABG, what the whole ABG is all about."