Australia on Wednesday confirmed that it has raised its concerns with India over the killing of a Sikh separatist leader in the Canadian westernmost province of British Colombia.

Speaking to reporters in New York on the sidelines of the UN General Assembly session, Foreign Minister Penny Wong, while responding to Canadian allegations that India was behind the killing of a Canadian citizen, said: "These are concerning reports."

“I note that investigations are still underway, but obviously these are concerning reports, and as I've said, we are monitoring these developments closely with our partners, and we'll continue to do so,” she said, according to a transcript published on the Foreign Ministry’s website.

When asked whether Australia has communicated its concerns with India, she said: "I will confirm that we have raised our concerns with India. I'm not going to go into any further detail on that."

Responding to the safety of Indian Sikhs in Australia, Wong said that her country allows peaceful expression of different views which is a key part of Australia's democracy

Sikh leader Hardeep Singh Nijjar was shot dead on June 18 in Surrey, British Columbia, in front of a Sikh temple. So far, no arrests have been made.

However, Canadian Prime Minister Justin Trudeau said on Monday that there are "credible allegations" that the Indian government was behind Nijjar's shooting death.

Nijjar was a vocal supporter of independence for a Khalistani state in the Punjab region. The Indian government has repeatedly insisted that Nijjar was a terrorist – a label his supporters denied – and at the recent G-20 summit in New Delhi, Prime Minister Narendra Modi chided Trudeau for allowing Sikh separatist protests in Canada.

Earlier on Monday, Canadian Foreign Affairs Minister Melanie Joly said a "top Indian diplomat" has been expelled from the country and expects India's full collaboration "to get to the bottom of this."

According to some media reports, the diplomat was Pavan Kumar Rai, who was allegedly associated with India's premier intelligence agency, the Research and Analysis Wing (RAW).

However, New Delhi has dismissed the allegation as "absurd," and has demanded that Ottawa take "prompt and effective legal action against all anti-India elements operating on their soil."

Later on Tuesday, in a tit-for-tat move, India ordered a senior Canadian diplomat in New Delhi to leave the country within five days.