The US on Tuesday said it is "deeply concerned" about the allegations made by Canadian Prime Minister Justin Trudeau on India's involvement in the killing of a Sikh separatist leader in Surrey, and urged New Delhi to "cooperate" with Canberra in the investigation of the incident.

Hardeep Singh Nijjar, 45, the chief of the banned Khalistan Tiger Force (KTF) and one of India's most-wanted terrorists who carried a cash reward of Rs 10 lakh on his head, was shot dead by two unidentified gunmen outside a gurdwara in Surrey in the western Canadian province of British Columbia on June 18.

Canadian Prime Minister Trudeau on Monday alleged the involvement of "agents of the Indian government" in the killing, claims outrightly rejected by New Delhi as "absurd" and "motivated".

“We are deeply concerned about the allegations referenced by PM Trudeau yesterday. We remain in regular contact with our Canadian partners,” a State Department spokesperson told PTI.

“It is critical that Canada’s investigation proceed and the perpetrators be brought to justice. We urge the Indian government to cooperate in the Canadian investigation and ensure that those responsible are held to account," the spokesperson said in response to a question.

"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 Monday in a speech to the House of Commons.

After Trudeau’s remarks in Parliament, Canadian Foreign Minister Melanie Joly confirmed that she has ordered the expulsion of "a senior Indian diplomat".

Reacting sharply to the allegations and Joly’s remarks, India on Tuesday rejected Trudeau’s claims, calling them "absurd and motivated".

The Ministry of External Affairs (MEA) has also asked a Canadian diplomat to leave India within the next five days.

“The decision (to expel a Canadian diplomat) reflects the Government of India’s growing concern at the interference of Canadian diplomats in our internal matters and their involvement in anti-India activities,” the MEA said in New Delhi.

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