India on Tuesday rejected the "absurd" allegation that its agents were behind the killing of a Sikh leader in Canada, after Prime Minister Justin Trudeau's bombshell accusation sent already sour diplomatic relations to a new low.
Ottawa also expelled a diplomat it described as the head of India's foreign intelligence service in Canada, prompting a tit-for-tat order from New Delhi for a Canadian diplomat to leave.
Trudeau said Monday that "credible allegations" linked Indian agents to the June slaying of Hardeep Singh Nijjar, who was accused by New Delhi of carrying out terrorist attacks in India -- a charge he denied before his death.
New Delhi insisted it had nothing to do with the killing, adding that Prime Minister Narendra Modi had "completely rejected" the accusation when earlier raised privately by Trudeau.
"Allegations of Government of India's involvement in any act of violence in Canada are absurd," the foreign ministry said in a statement.
"We are a democratic polity with a strong commitment to rule of law."
Nijjar, whom India had declared a wanted terrorist, was gunned down on June 18 in Surrey, a suburb of Vancouver home to a large Sikh community.
Canada has the largest population of Sikhs globally outside of India, and New Delhi has long been unhappy with Canada's handling of Sikh separatist activists.
Nijjar was part of a movement that advocated for the creation of an independent Sikh state to be carved out of part of northern India and perhaps part of Pakistan.
India has long claimed that Nijjar was involved in violent attacks on its soil, including a 2007 bombing that killed six people in the city of Ludhiana.
Trudeau made the allegation public before an emergency session of parliament, calling in the "strongest possible terms" for the Indian government to cooperate in clearing up the matter.
"The involvement of any foreign government in the murder of a Canadian citizen on Canadian soil is an unacceptable violation of our sovereignty," he said.
Foreign Minister Melanie Joly then announced the expulsion of the local head of the Research and Analysis Wing (RAW), India's foreign intelligence agency.
India responded by summoning Canada's High Commissioner to the foreign ministry on Tuesday before announcing a reciprocal expulsion of an unnamed top Canadian diplomat.
That decision reflected the "growing concern at the interference of Canadian diplomats in our internal matters and their involvement in anti-India activities", the ministry said.
The Canadian High Commission in New Delhi declined to comment when contacted by AFP.
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Tensions between India and Canada have been simmering over the unsolved slaying, and Indian unhappiness over how Ottawa has handled Sikh separatists.
Jocelyn Coulon, a former adviser to Trudeau who is now an independent researcher, said Canada's accusation would have "the effect of a bomb around the world".
India will join "the group of nations that assassinate political opponents" abroad, much as Saudi Arabia orchestrated the murder of journalist Jamal Khashoggi in Turkey in 2018, said Coulon.
Trudeau was in New Delhi last week for the G20 summit and met privately with his Indian counterpart but his visit was a testament to the strained ties between their countries.
Modi expressed "strong concerns about continuing anti-India activities of extremist elements in Canada" during a meeting with Trudeau, according to an Indian government statement.
India has often complained about activities of the Sikh diaspora abroad, particularly in Canada, which New Delhi believes could revive a Sikh separatist movement.
The Indian state of Punjab, which is 58 percent Sikh and 39 percent Hindu, was rocked by a violent separatist movement in the 1980s and early 1990s, in which thousands died.
Canada also recently suspended negotiations for a free-trade agreement with India.
Trudeau later told the media that Canada would always defend "freedom of expression, freedom of conscience and freedom of peaceful protest" while acting against hatred.