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ordering the expulsion of six high-ranking Canadian diplomats, including the acting high commissioner, and said it had withdrawn its envoy from Canada, contradicting Canada's statement of expulsion.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

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.

India said it had asked six Canadian diplomats to leave by Saturday. The ministry also said it had summoned Acting High Commissioner in India Stewart Wheeler, currently Canada's top diplomat in the South Asian country.

India said it was withdrawing its diplomats from Canada because it was not confident that their safety could be guaranteed.

"We have no faith in the current Canadian Government's commitment to ensure their security. Therefore, the Government of India has decided to withdraw the High Commissioner and other targeted diplomats and officials," India's foreign ministry said in a statement.

Major rupture

Canada's Foreign Minister Melanie Joly said the government had requested India to remove the diplomatic immunity of six diplomats so that the Canadian investigative agencies could question them regarding the allegations of criminal activity.

But since India did not co-operate, it had to expel the diplomats.

"We're not seeking diplomatic confrontation with India," she said. "But we will not sit quietly as agents of any country are linked to efforts to threaten, harass or even kill Canadians."

Canada withdrew more than 40 diplomats from India in October 2023 after New Delhi asked Ottawa to reduce its diplomatic presence.

"We have gone from a rift to a major rupture in the relationship with India," Fen Osler Hampson, professor of international relations at Ottawa's Carleton University said in a telephone interview. "It is hard to see at this juncture that a return to normalcy will happen any time in the foreseeable future."

Canada is home to the highest population of Sikhs outside their home state of Punjab and demonstrations in recent years have irked India's government

The US has also alleged that Indian agents were involved in an attempted assassination plot against another Sikh separatist leader in New York last year, and said it had indicted an Indian national working at the behest of an unnamed Indian government official.

An Indian government committee investigating Indian involvement in the foiled murder plot will meet US officials in Washington this week, the State Department said on Monday.

The accusations of assassination plots against Sikh separatist leaders in Canada and the US have tested their relationship with India as they look to forge deeper ties with the country to counter China's rising global influence.