Canada expelled six Indian diplomats including the high commissioner on Monday, linking them to the murder of a Sikh separatist leader and alleging a broader effort to target Indian dissidents in Canada.

Earlier in the day, India retaliated by ordering the expulsion of six high-ranking Canadian diplomats including the acting high commissioner and said it had withdrawn its envoy from Canada, contradicting Canada's statement of expulsion.

The diplomatic row represents a major deterioration of relations between the two Commonwealth countries. Ties have been frayed since Canadian Prime Minister Justin Trudeau said last year he had evidence linking Indian agents to the assassination of Sikh leader Hardeep Singh Nijjar on Canadian territory.