Canada has ordered an Indian diplomat leave the country as it investigates the killing of a prominent Canadian Sikh leader who was shot in British Columbia in June.
Canadian Prime Minister Justin Trudeau said that an investigation into "credible allegations" that Indian state actors could be behind the death of Hardeep Singh Nijjar was ongoing.
Ottowa's Foreign Minister Melanie Joly said: "If proven true this would be a great violation of our sovereignty and of the most basic rule of how countries deal with each other."
"As a consequence we have expelled a top Indian diplomat," Joy said without stating exactly whom.
Canada is home to hundreds of thousands of people of Indian origin, many of whom are Sikhs.
The White House National Security Council spokesperson Adrienne Watson said in a statement the United States was "deeply concerned about the allegations" made by Canada.
"We remain in regular contact with our Canadian partners. It is critical that Canada's investigation proceeds and the perpetrators be brought to justice," the statement read.
India rejects allegations
India's Ministry of External Affairs said in a statement that: "Allegations of the Government of India's involvement in any act of violence in Canada are absurd and motivated."
Such "allegations seek to shift the focus from Khalistani terrorists and extremists, who have been provided shelter in Canada and continue to threaten India's sovereignty and territorial integrity," it said.
Who is the Sikh leader in question and what is the issue?
Hardeep Singh Nijjar was shot on the premises of a Sikh temple in Surrey, British Columbia, in June of this year.
Nijjar was declared a terrorist by the Indian government a few years ago because of his activism for a separate homeland for Sikhs in the Punjab region of India.
The fight for a separate Sikh state or the "Khalistan" movement has its roots in the partition of the Indian subcontinent along religious lines.
The 1947 partition sent Muslims to the newly created Pakistan and Hindus and Sikhs to India. Punjab province, which was divided between India and Pakistan, saw deadly violence.
The Khalistan movement was crushed by the Indian government in the years that followed, especially in the 1980s. The decade saw violent anti-Sikh riots that killed thousands, and the movement was banned, with Indian officials citing it as a security threat.
Trudeau spoke to Modi at G20
The Indian government had put Nijjar on a wanted list and accused him of being actively involved in the networking and training of the separatist group he headed.
Many in Canada and elsewhere alleged that the Indian government was behind the death of Nijjar. Trudeau said intelligence agencies were looking into those allegations.
"Over the past number of weeks Canadian security agencies have been actively pursuing credible allegations of a potential link between agents of the government of India and the killing of a Canadian citizen, Hardeep Singh Nijjar," Trudeau said.
Trudeau added that he brought up the slaying with Modi at the G20 summit. Trudeau said he told Modi that any Indian government involvement would be unacceptable and that he asked for cooperation in the investigation.
The Indian government in its response to the conversation between the leaders said that allegations at the time were also "completely rejected."