The United States is in communication with India on Canada's allegations that New Delhi was potentially involved in the killing of a Sikh separatist leader on Canadian soil, the White House has said.

The US also remains in regular contact with the Canadian government, White House Press Secretary Karine Jean-Pierre said on Friday.

A diplomatic row erupted between India and Canada following Canadian Prime Minister Justin Trudeau's allegations of "potential" involvement of Indian agents in the killing of Khalistani extremist Hardeep Singh Nijjar, a Canadian citizen, in British Columbia on June 18.

India has rejected the allegations as "absurd" and "motivated" and expelled a senior Canadian diplomat in a tit-for-tat move to Ottawa's expulsion of an Indian official over the case.

"We have engaged with the Indian government. But certainly, we're not going to get into our private diplomatic conversations. But, yes, there have been conversations with our partners in the Indian government," Jean-Pierre told reporters at her daily news conference.

"Obviously, we are deeply concerned, as he said as well... what the Prime Minister (of Canada) has referenced here. And so, we remain in regular contact with the Canadian... government and the Canadian partners," she said.

Responding to questions, Jean-Pierre said she would not comment on diplomatic conversations.

Earlier this week, the US had said that it supports Canada's efforts to investigate allegations of India's involvement in the killing of Nijjar, observing that no country can get any "special exemption" for such kind of activities.

While Canada hasn't yet provided any public evidence to back its claims, a media report said citing Canadian government sources that Ottawa's allegations are based on both human and signals intelligence and inputs from an ally the Five Eye intelligence network.

The Five Eyes network is an intelligence alliance consisting of the United States, the United Kingdom, Australia, Canada and New Zealand.

In a reflection of hardening of its position, India on Wednesday advised all its nationals living in Canada and those contemplating travelling there to exercise "utmost caution" in view of growing anti-India activities and "politically-condoned" hate crimes as well as "criminal violence" in that country.

Prime Minister Trudeau on Thursday said Canada is not looking to "provoke or cause problems" with India as he urged New Delhi to take the matter "extremely seriously" and work with Ottawa to "uncover the truth".

The India-Canada ties have been reeling under some strain for the last few months in view of increasing activities of the pro-Khalistani elements in the North American country. India believes the Trudeau government is not addressing its genuine concerns.

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