EIghty years since his martyrdom during the Second World War a preacher from Papua New Guinea has become the first saint of the Pacific.

Pope Leo XIV canonised Peter ToRot, a catechist for the Catholic church, at mass on Sunday inside St Peter's Square basilica in Rome.

The ceremony was the final step of the process that the late Pope Francis had approved after a vote of cardinals and bishops in one of his final acts as pope.

Pope John Paul II in 1995 during a papal visit to PNG declared that Mr ToRot had lived a holy life in a beatification, the first major sign that the Vatican would one day celebrate the son of a village chief as a saint.

Raised at Rakunai village on the island of New Britain, Mr ToRot fronted a Catholic mission as the Imperial Japanese military forces occupied New Guinea from 1941.

He was arrested and held in a Japanese-run prison in 1945 for practising Catholicism against orders, and he defiantly continued to spread the word of God among his followers.

The 33-year-old old was later given a lethal injection for resisting orders.

Several thousand dedicated Papuans and other Melanesian Catholics are said to have travelled to Rome to join more than 50,000 people for the mass ceremony.

Archbishop Rochus Tatamai of Rabaul in the East New Britain province spoke on behalf of Mr ToRot's family.

"My parents and my grandparents would tell us about his unwavering commitment to God and community," Archbishop Tatamai said in a Vatican statement.

"It wasn't just history; it was a living example."

Archbishop Tatamai hopes Mr ToRot's actions will inspire Papuan families to show that "holiness is possible in ordinary life".

"His life has taught me that faith is not abstract - it is lived, sometimes in the most challenging circumstances," he said.

The archbishop called the canonisation of his great uncle as "far more than a Church celebration".

The timing of the sainthood has added an important element to Papua New Guinea's celebrations of 50 years of independence from Australia.

Civic and religious leaders have framed the canonisation as a "gift to our country" amid its Jubilee year of hope.

"It is a blessing for the whole country, reminding us that society itself depends on the strength of families," Archbishop Tatamai said.

"It is a gift to our country as a national revolutionary that calls us to holiness that begins from the family and extends to the whole society.

"(Peter ToRot) was known for humility, service to the poor, devotion to prayer, and respect for elders.

"He challenges every one of us to live lives of service and generosity - ToRot's own story offers practical guidance."

The Archbishop belongs to the Missionaries of the Sacred Heart, an order of the Catholic Church that Mr ToRot served and took over the pastoral duties of the local priest who evacuated New Guinea during the height of World War II.

Mr ToRot was among seven saints from around the globe who were canonised in the ceremony the Roman Catholic Church observes as Mission Sunday.