Canadian Prime Minister Justin Trudeau on Wednesday said India made “a horrific mistake” by thinking it could interfere as aggressively as it allegedly did in Canada’s sovereignty.

Trudeau made the remark two days after Canada kicked out six Indian diplomats, linking them to the murder of a Sikh separatist leader in Canada and alleging a broader effort to target Indian dissidents in the country.

The Canadian leader’s comments were the strongest he has made in a year-long dispute that plunged bilateral relations to a new low.

“The Indian government made a horrific mistake in thinking that they could interfere as aggressively as they did in the safety and sovereignty of Canada,” he told an independent probe into foreign interference in Canadian politics.

Trudeau said Ottawa could take further steps to ensure Canadians’ security but declined to give details.

India denies the allegations of interference and has expelled six Canadian diplomats in a tit-for-tat move.