With every passing day, there is a new revelation in the diplomatic row between India and Canada.

Now, Canada has shared evidence that Indian government agents were potentially involved in the murder of Sikh separatist leader Hardeep Singh Nijjar in British Columbia with New Delhi weeks ago, Prime Minister Justin Trudeau said on Friday.

"Canada has shared the credible allegations that I talked about on Monday with India. We did that many weeks ago," Mr. Trudeau told a news conference in Ottawa. "We are there to work constructively with India. We hope that they engage with us so that we can get to the bottom of this very serious matter."

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

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

However, Mr. Trudeau has not provided any details about what Canada's spy agencies have collected, and his office has not confirmed or denied the CBC report.

U.S. Secretary of State Antony Blinken said on Friday the United States wanted to see "accountability" over the killing.

"We are deeply concerned about the allegations that Prime Minister Trudeau has raised," Mr. Blinken told reporters in a press briefing. The White House has raised similar concerns, but Mr. Blinken is the most senior U.S. official to have commented on the issue thus far.