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, Paralel.Az reports citing Reuters.

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ordering the expulsion of six high-ranking Canadian diplomats including the acting high commissioner and said it had withdrawn its envoy from Canada, contradicting Canada's statement of expulsion.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

The government now has "clear and compelling evidence that agents of the government of India have engaged in and continue to engage in activities that pose a significant threat to public safety," Trudeau said at a news conference.

These activities involved clandestine information gathering techniques, coercive behaviour, targeting South Asian Canadians and involvement in over a dozen threatening and violent acts, including murder, he said.

"This is unacceptable," he said, adding that India had committed a fundamental error by engaging in criminal activities in Canada.

India has long denied Trudeau's accusations. On Monday, it dismissed Canada's move on the inquiry and accused Trudeau of pursuing a "political agenda."

The Royal Canadian Mounted Police said in an earlier news conference the government of India had undertaken a broad campaign against Indian dissidents including homicides and extortion. It had also used organised crime to target the South Asian community in Canada and interfered in democratic processes, police said.

"The decision to expel these individuals was made with great consideration and only after the RCMP gathered ample, clear and concrete evidence which identified six individuals as persons of interest in the Nijjar case," the foreign ministry said in a statement.