Intelligence gained by the "Five Eyes" network led to Canada's public accusation that the Indian government may have played a role in the assassination of a Sikh separatist activist on Canadian soil, the US Ambassador to Canada said Sunday.

I'm "confirming that there was shared intelligence among Five Eyes partners that helped led Canada to making the statements that the prime minister made," US Ambassador to Canada, David Cohen, told CTV's Question Period with Vassy Kapelos in a Sunday interview.

Five Eyes is an intelligence sharing pact between the United States, United Kingdom, Canada, Australia and New Zealand, though the ambassador would not confirm if that shared intelligence came from the US. "I'm not. I wouldn't in any circumstance," Cohen said.

Relations between India and Canada plummeted last week after Canadian Prime Minister Justin Trudeau said authorities had been investigating "credible allegations" that India was potentially behind the June killing of Hardeep Singh Nijjar, a Sikh separatist activist, who was gunned down by two masked men in Surrey, British Columbia.

India has vehemently denied the claims, calling them "absurd and motivated." India's foreign ministry spokesperson Arindam Bagchi said Canada has provided "no specific information" to support the allegations.

Both nations have expelled senior diplomats in reciprocal moves, raising the prospect of an awkward rift between key partners of the US.

The spat then escalated further last week when India suspended visa services for Canadian citizens over what it said were "security threats" against diplomats in Canada.

Speaking to CTV, Cohen said the US did express its concern to India over the allegations and asked India to cooperate with Canada in its investigation.

"If they prove to be true, it is a potentially a very serious breach of the rules based international order," the ambassador said.

Trudeau on Thursday called on India to work with Canada and to "shed full transparency, ensure accountability and justice in this manner."

"We call upon the government of India to work with us. To take seriously these allegations and to allow justice to follow its course," the prime minister said at the Canada Mission in the United Nations.

Trudeau said Canada is not looking to provoke or cause problems but said its justice system, "and robust processes will follow its course," in regard to investigating into the allegation.

In a strongly worded statement to reporters Thursday, Bagchi called Canada a "safe haven for terrorists" and that Canada needed to "worry about its international reputation" in the wake of its explosive allegations.

Bagchi, said the suspension of visa services to Canadian nationals was because of Canadian authorities "incitement of violence" and "inaction."

"The creation of an environment that disrupts the functioning our high commission and consulates, that's what's making us stop temporarily the issuance of visas or providing visa services," Bagchi, said.

Militancy or campaigning?

The Indian government has long accused Canada of inaction in dealing with what it said is Sikh separatist extremism aimed at creating a separate Sikh homeland that would be known as Khalistan and include parts of India's Punjab state.

Nijjar was an outspoken supporter of the creation of Khalistan. India considers calls for Khalistan a grave national security threat.

A number of groups associated with the idea of Khalistan are listed as "terrorist organizations" under India's Unlawful Activities (Prevention) Act (UAPA). Nijjar's name appears on the list of UAPA terrorists and in 2020, the Indian National Investigation Agency accused him of "trying to radicalize the Sikh community across the world in favor of the creation of 'Khalistan.'"

Several Sikh organizations overseas say the movement is being falsely equated with terrorism by the Indian government, and say they will continue to peacefully advocate for the creation of Khalistan, while bringing to light what they say is years of human rights abuses faced by the community in India.

According to local police, Nijjar was gunned down in his truck in June by two masked killers outside a Sikh temple in Surrey, British Columbia.

His death both shocked and outraged the Sikh community in Canada, one of the largest outside India and home to more than 770,000 members of the religious minority.

Canadian police have not arrested anyone in connection with Nijjar's murder. But in an August update, police released a statement saying they were investigating three suspects and issued a description of a possible getaway vehicle, asking for the public's help.