An American official has supported a call by Canadian Prime Minister Justin Trudeau for India to cooperate in the investigation of a Sikh leader's assassination in Vancouver in June.

"We want to see accountability. And it's important that the investigation run its course and lead to that result," US Secretary of State Antony Blinken told reporters in New York, where he was taking part in the United Nations General Assembly.

"We would hope that our Indian friends would cooperate with that investigation as well," Blinken said, referring to Canadian citizen Hardeep Singh Nijjar.

Nijjar, who was wanted in India for alleged terrorism and conspiracy to commit murder, was shot dead by two masked assailants.

Blinken's statement came four days after Trudeau linked Indian intelligence agents to the murder of the activist campaigning for the creation of a Sikh homeland called Khalistan.

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.

Following Trudeau's bombshell, Sikh leaders in Canada demanded justice for Nijjar's killing.

"We want a full investigation that brings to justice the people involved in this assassination, including those who pulled the trigger and the ones who plotted this assassination," Harkirt Singh Dhadda, a lawyer and prominent member of the Sikh community in the Toronto area, said.

Nijjar's son also demanded the arrest of his father's killers.

"Hopefully, you can take this a step further and get specific individuals," Balraj Singh Nijjar told reporters.

Jaskaran Sandhu, co-founder of Baaz News, a website for the Sikh community, warned that "if the government doesn't take a strong stance and send a strong message, all it declares to the world is that it's open season on our citizens."

Jagmett Singh, the leader of the left-wing New Democratic Party and a Trudeau ally said Trudeau's announcement confirms suspicions that India was interfering in the democratic rights of Canadians.

Canada must also put an end to intelligence sharing with New Delhi, Sikh officials said.

Since 2018, the two countries have established cooperation on counter-terrorism activities which commits them to financial, judicial and police cooperation — an agreement eyed warily by 770,000 Canadian Sikhs today.

  WITH AFP