Canada, US worked closely on possible India link to Hardeep Singh Nijjar killing

• Canadian govt source says evidence to be provided "in due course."
• India-Canada diplomatic ties face further strain.
• Normal discussion between both nations seems difficult.

A senior Canadian government source revealed on Tuesday that Canada and the US collaborated "very closely" to investigate intel suggesting that Indian operatives may have been involved in the murder of Hardeep Singh Nijjar in British Columbia earlier this year.

The shooting of Nijjar, 45, in June, according to credible reports, was subject to a thorough investigation by domestic security agencies, according to Canadian Prime Minister Justin Trudeau's announcement on Monday.

According to the source, "We've been working with the US very closely, including on the public disclosure yesterday."

The official, who spoke on the condition of anonymity owing to the sensitivity of the issue, also stated that the evidence that Canada is in possession of would be provided "in due course," Reuters reported.

On Tuesday, Trudeau told reporters that the case had important implications for international law.

He also urged the Indian government to take the situation seriously and support a thorough investigation by Canada.

India instantly denounced Trudeau's claim as ludicrous and announced it was expelling a Canadian diplomat in retaliation for Canada's Monday expulsion of India's top intelligence official.

As New Delhi is upset about Sikh revolutionary activity in Canada, the controversy further strains already strained diplomatic ties between both nations.

"I would expect that normal discussions between the two governments will be difficult while this issue is being resolved," said Roland Paris, Trudeau's former foreign policy adviser and a professor of international affairs at the University of Ottawa.