Canada's Prime Minister Justin Trudeau (left) walks past Indian Prime Minister Narendra Modi as they take part in a wreath-laying ceremony at Raj Ghat, Mahatma Gandhi's cremation site, during the G20 Summit in New Delhi, Sept 10, 2023. (PHOTO / AP)

NEW DELHI/NEW YORK - Canadian Prime Minister Justin Trudeau on Thursday called on India to cooperate with an investigation into the murder of a Sikh separatist leader in British Columbia as New Delhi asked Ottawa to reduce the number of its diplomats.

Trudeau said on Monday that Ottawa had credible allegations linking Indian government agents to the murder of Hardeep Singh Nijjar in June, prompting an angry reaction from New Delhi. Nijjar, 45, was a Canadian citizen.

The Canadian government has amassed both human and signals intelligence in a months-long investigation into the Sikh separatist leader's murder, CBC News separately reported on Thursday citing sources.

The United States is in touch with both Canada and India over Ottawa's allegations, US national security adviser Jake Sullivan said on Thursday, confirming for the first time that Washington was talking to New Delhi about the matter

Traditional Canadian allies have so far taken a relatively cautious approach to the matter. 

ALSO READ: India suspends visas for Canadian citizens amid diplomatic row

"There is no question that India is a country of growing importance and a country that we need to continue to work with ... and we're not looking to provoke or cause problems," Trudeau said in a press conference in New York on the sidelines of the annual high-level United Nations General Assembly. "But we are unequivocal around the importance of the rule of law and unequivocal about the importance of protecting Canadians."

"That's why we call upon the government of India to work with us to establish processes to discover and to uncover the truth of the matter."

The CBC report said, citing Canadian sources, that no Indian official, when pressed behind closed doors has denied the allegation that there is evidence suggesting Indian government involvement in Nijjar's death. India's Ministry of External Affairs did not immediately respond to a Reuters request for comment on the CBC report.

ALSO READ: Trudeau: Canada wants answers from India over slain Sikh leader

The report said the intelligence included communications involving Indian officials, among them Indian diplomats present in Canada, adding that some of the intelligence was provided by an unidentified ally in the Five Eyes alliance.

Five Eyes is an intelligence-sharing network that includes the US, the UK, Canada, Australia and New Zealand.

The United States is in touch with both Canada and India over Ottawa's allegations, US national security adviser Jake Sullivan said on Thursday, confirming for the first time that Washington was talking to New Delhi about the matter.

"There's not some special exemption you get for actions like this," Sullivan told reporters when asked about Trudeau's statement about possible Indian involvement. "It is a matter of concern for us, it is something we take seriously."

An image of former Gurdwara President Hardeep Singh Nijjar is displayed at the Guru Nanak Sikh Gurdwara temple in Surrey, British Columbia, Canada, on Sept 19, 2023. (PHOTO / AFP)

US President Joe Biden and several members of the Five Eyes raised the murder of Hardeep Singh Nijjar with Indian Prime Minister Narendra Modi when they met at the G20 this month, the Financial Times reported on Thursday.

The Indian foreign ministry said Canada had not shared any specific information about the murder. Nijjar supported a Sikh homeland in the form of an independent Khalistani state and was designated by India as a "terrorist" in July 2020.

"As a country with a strong and independent justice system, we allow those justice processes to unfold themselves with the utmost integrity," Trudeau replied when asked when Canada would release the evidence it had.

'Reduction' in diplomats

Seperately, the Indian government on Thursday said it had asked Canada to reduce the number of its diplomats posted in India amid a diplomatic row, according to official sources.

New Delhi cited the "interference of Canadian diplomats in Indian affairs" as the reason for the move.

India has issued an advisory to Indians living in Canada, urging them to exercise utmost caution

"The Canadian diplomatic presence in India is larger than what India has and accordingly needs to be downsized," India's foreign ministry spokesperson Arindam Bagchi told media.

"We have informed the Canadian government that there should be parity in diplomatic presence. Their numbers are very much higher than ours in Canada."

The step came hours after India suspended visa services in Canada.

ALSO READ: India tells citizens in Canada to exercise caution as ties worsen

India has issued an advisory to Indians living in Canada, urging them to exercise utmost caution.

Canada has suspended talks on a trade deal with India.