Canada said on Monday it had credible information linking Indian government agents to the murder of a Sikh separatist leader in British Columbia in June and said it had expelled a senior Indian intelligence official.
The announcement marks a significant worsening of bilateral ties at a time when India is already unhappy that Canadian authorities are not cracking down on Sikh protesters who want their own independent homeland.
Prime Minister Justin Trudeau said any involvement of a foreign government in the killing of a Canadian citizen was "an unacceptable violation of our sovereignty".
Hardeep Singh Nijjar, was shot dead outside a Sikh temple in Surrey, British Columbia, on June 18.
Nijjar supported a Sikh homeland in the form of an independent Khalistani state and was designated by India as a "terrorist" in July 2020, India's The Tribune newspaper said.
"Canadian security agencies have been actively pursuing credible allegations of a potential link between agents of the government of India" and Nijjar's death, Trudeau said in an emergency statement to the House of Commons.
"Canada has declared its deep concerns to the top intelligence and security officials of the Indian government.
Last week at the G20 I brought them personally and directly to Prime Minister Modi in no uncertain terms."
The Indian high commission (embassy) in Ottawa did not respond to requests for comment.
New Delhi said last week that Modi had conveyed strong concerns about protests in Canada against India to Trudeau.
Canada has the highest population of Sikhs outside their home state of Punjab in India, and the country has been the site of many demonstrations that have irked India.
Canada is home to one of the largest overseas communities of Indian origin, which number approximately 1.4 million out of an overall Canadian population of 40 million. About 770,000 people reported Sikhism as their religion in the 2021 Census.
The two countries, which earlier this year said they could agree the outlines of a trade deal by end-2023, have now frozen talks on the agreement. Canada gave few details while India cited "certain political developments."
Bilateral trade in 2022 amounted to just C$13.7 billion out of a total of C$1.52 trillion, according to Statistics Canada.
Trudeau did not directly accuse India of definitely being involved and Foreign Minister Melanie Joly later used more cautious language, saying "if proven true" the allegations would be unacceptable.
Joly told reporters that Ottawa had expelled the Indian head of intelligence in Canada but gave no further details.
"In the strongest possible terms, I continue to urge the government of India to cooperate with Canada to get to the bottom of this matter," said Trudeau.
Public Safety Minister Dominic LeBlanc said several senior Canadian government officials had visited India recently to express Ottawa's concerns.
In April, India asked Britain for increased monitoring of UK-based supporters of a Sikh separatist movement. New Delhi was upset after protesters carrying "Khalistan" banners detached the Indian flag from the diplomatic mission's building in London.
