The Fiji-based Pacific Concerns Resource Centre says the death of Joseph Kabui is a tremendous loss to Bougainville.
Mr Kabui, the first president of an autonomous Bougainville, died in hospital in Buka of a suspected heart attack.
Rex Rumakiek says his death is tragic, and untimely.
He says Mr Kabui was a leader of the people, and was known for his skill at reconciliation.
"His inspiration will remain with the people and whatever leaders there are in the future, will be measured on his leadership capabilities. Obviously leaders will copy his style of leadership for unity, reconciliation and peace."
Rex Rumakiek .