Pope Francis has apologised to indigenous people for abuse committed at church-run residential schools in Canada, and said he hoped to visit the country in July.

"I ask for God's forgiveness for the deplorable conduct of these members of the Catholic Church," he said, telling indigenous delegations at the Vatican it caused him "pain and shame".

Numerous investigations into the former residential schools are under way across Canada after the discovery of mass unmarked graves, with more than 4,000 children believed to be missing, according to authorities.

Francis said he heard "stories of suffering, deprivation, discriminatory treatment and various forms of abuse" during meetings this week with survivors from the First Nations, Metis and Inuit groups.

"I join the Canadian bishops in asking you for forgiveness," he said.

The 85-year old said "I hope" to travel to Canada for the country's St Anne's Feast Day on 26 July.

"The pope's words were necessary and I deeply appreciate them," Cassidy Caron, president of the Metis National Council, told journalists after the meeting.

"I now look forward to his coming to Canada where he can deliver this heartfelt apology directly to our survivors and their families," she said.

Francis heard first-hand this week of centuries of abuse committed at the schools, and the delegations had pressed him for an apology for a scandal that rocked the Catholic Church.

Some 150,000 First Nations, Metis and Inuit children were enrolled from the late 1800s to the 1990s in 139 residential schools across Canada, as part of a government policy of forced assimilation.

They spent months or years isolated from their families, language and culture, and many were physically and sexually abused by headmasters and teachers.

Francis slammed the "ideological colonisation" of which "so many children have been victims".

"Your identity and culture have been wounded, many families have been separated," he said.

He described as "chilling" the "unresolved traumas that have become intergenerational traumas".

Thousands are believed to have died of disease, malnutrition or neglect. More than 1,300 unmarked graves have been discovered since May 2021 at the schools.

A truth and reconciliation commission concluded in 2015 the failed government policy amounted to "cultural genocide".

In January, Canada announced a $31.5bn agreement to reform its discriminatory child welfare system and compensate Indigenous families who suffered because of it.