Church service to mark eight centuries since Synod of Oxford brings together chief rabbi, senior Anglicans and Roman Catholic bishop.
Justin Welby visited survivors in Prince Albert, Sask. on Sunday, then heads to Toronto Monday.
Indigenous leaders in Canada say Catholic Church must take concrete action to support survivors and prevent more harm.
'I ask for forgiveness from God for this reprehensible conduct by some members of the Church,' says Pope Francis.
