Pope Francis left Rome on Sunday for a trip to Canada to apologise for the role of the Roman Catholic Church in residential schools where many indigenous children were abused.

The 85-year-old pope, his entourage and journalists flew out of Rome's Fiumicino airport on an ITA Italian airline plane en route to Edmonton, capital of Alberta.

The week-long trip will include at least five encounters with native people as Francis makes good on a promise to apologise on their home territory for the Church's role in the state-sanctioned schools, which sought to erase indigenous cultures.

It also will be a test of pope's health. He had to cancel a trip to Democratic Republic of Congo and South Sudan in early July because of a knee problem that forced him to use first a wheel chair and later a cane.

In an exclusive interview with Reuters this month, Francis  gave details of his ailment for the first time in public, saying he had suffered "a small fracture" in the knee when he took a misstep while a ligament was inflamed.