The United States, the United Kingdom and Australia on Tuesday expressed concerns after Canadian Prime Minister Justin Trudeau alleged that the India may have been involved in the assassination of a Sikh separatist leader on the country’s soil.

Trudeau on Monday told Parliament that Canadian intelligence agencies were actively pursuing “credible allegations” tying Indian agents to the shooting of Hardeep Singh Nijjar, a 45-year-old Sikh leader who was killed by masked gunmen on June 18 in Surrey, outside Vancouver.

India quickly dismissed Trudeau’s claims as “motivated” and asked Canada instead to take legal action against “anti-Indian elements” operating from its soil. It also expelled a Canadian diplomat, in a tit-for-tat move after Canada expelled an official of the Indian foreign intelligence service.

While Canada has not yet made public any evidence of India’s involvement in Nijjar’s death, its foreign ministry said that Trudeau took up the matter with US President Joe Biden and British Prime Minister Rishi Sunak.

The White House has said that the US was “deeply concerned” about the allegations of the murder and it was critical that the perpetrators be brought to justice.

“We think it’s important there is a full and open investigation and we would urge the Indian government to cooperate with that investigation,” a senior State Department official added, according to Reuters.

An unidentified senior Canadian official told the news agency that Canada has been working “very closely” with the US in the case and the evidence with the Canadian intelligence will be shared in “due course”.

British Foreign Secretary James Cleverly said it was important for the Canadian investigation to run its course to determine whether India was involved in the killing of Nijjar.

“All countries should respect sovereignty and the rule of law,” he wrote on X, formerly known as Twitter. “We are in regular contact with our Canadian partners about serious allegations raised in the Canadian Parliament.”

Cleverly told AFP that he expects India to fully cooperate in the inquiry, adding that Britain has a “very strong relationship” with both India and Canada.

He refused to say if Britain would suspend trade talks with India and that it would be “unhelpful” to speculate on the outcome of the investigation that is being carried out by Canada.

Australian Foreign Minister Penny Wong said her country is “deeply concerned” by the allegations and had raised the issues with India.

Nijjar was a strong supporter of Khalistan, an independent Sikh state sought by some groups. He was the head of the Khalistan Tiger Force, which is designated a terrorist outfit in India. Nijjar was also among India’s most wanted persons.

Trudeau’s accusations mark a significant escalation in tensions between Canada and India, both G20 members. New Delhi has long accused Ottawa of giving free rein to Sikh separatists.

Also read: Allegations of Khalistani separatist’s assassination signal a collapse in India-Canada ties