Prime Minister Justin Trudeau says he chose to reveal a possible link between the Indian government and the killing of a Canadian to "put a chill" on India amid concerns in the Sikh community over safety.

In September, Trudeau told the House of Commons there was credible intelligence linking India to the June 18 shooting death of Sikh activist Hardeep Singh Nijjar in the parking lot of his gurdwara in Surrey, B.C.

Trudeau says in a year-end interview with The Canadian Press that the sombre message he delivered publicly that day was intended as an extra "level of deterrence" to keep Canadians safer. India's government has continued to deny any connection to the killing.

Trudeau says the Sikh community in B.C. was worried about what could happen next, and that his public statement came after "quiet diplomacy" that included raising the allegations with India at the highest levels. He says he also expected that information would be published in the media, and he wanted Canadians to hear directly from him that the government was on top of the situation.