Canadian national security agencies are investigating "credible allegations" that “agents of the government of India” were involved in the death of a Canadian Sikh leader in June, Canada's Prime Minister Justin Trudeau announced Monday.

Trudeau said that steps are being taken to hold the people accountable behind the death of prominent Sikh leader Hardeep Singh Nijjar in British Columbia.

"Canada is a rule of law country, the protection of our citizens in [defense] of our sovereignty are fundamental," Trudeau said in a statement addressing the House of Commons. "Our top priorities have therefore been one, that our law enforcement and security agencies ensure the continued safety of all Canadians."

Melany Joly, Canada's foreign affairs minister, announced the country will oust a "key Indian diplomat" and anticipated India to "fully collaborate" with Canada to get answers, according to CTV News.

Nijjar was killed on June 18 near a Sikh cultural center in Surrey, British Columbia, according to The Associated Press.

He advocated for the creation of Khalistan, an independent Sikh homeland in India's Punjab region, according to CTV News.

Sikhs in Canada protested over Nijjar's death, accusing the Indian government of being behind the slaying, according to CTV News.

The Indian Embassy in Washington, D.C., did not immediately respond to ABC News' request for comment.

Trudeau told the House of Commons he brought his concerns directly to India's Prime Minister Narendra Modi at last week's G-20 summit in New Delhi.

"Any involvement of a foreign government in the killing of a Canadian citizen on Canadian soil is an unacceptable violation of our sovereignty," Trudeau said.

Canadian Trade Minister Mary Ng said Friday she's postponing a trade mission to India that was scheduled for October, after tensions between the two countries escalated after Modi reprimanded Trudeau during the G-20 summit, according to Reuters.