Canada is investigating allegations that India was involved in the assassination of a Sikh activist, a Canadian citizen, on Canadian soil. 

The victim, Sikh leader Hardeep Singh Nijjar, was gunned down outside a Sikh cultural center in Surrey, British Columbia on June 18. 

Nijjar was a strong supporter of an independent Sikh homeland known as Khalistan. The movement is banned in India as officials see it as a national security threat. But the movement still has some support in countries like Canada and the United Kingdom, where sizable Sikh communities live.

Prime Minister Justin Trudeau said Canadian intelligence agencies are investigating allegations that the government of Indian Prime Minister Narendra Modi may have played a role in Nijjar’s assassination. 

Trudeau told Parliament Monday he’d discussed the matter with Modi at the G-20 last week. He said he told Modi that any involvement would be unacceptable and that he asked for cooperation in the investigation.

“Any involvement of a foreign government in the killing of a Canadian citizen on Canadian soil is an unacceptable violation of our sovereignty,” Trudeau said.