India said it was told by Canadian authorities that its top diplomat in Ottawa is a “person of interest” in an investigation involving the murder of a Sikh activist last year, further straining ties between the two governments.

New Delhi received notice via a diplomatic communication that India’s High Commissioner to Canada, Sanjay Kumar Verma, as well as other Indian diplomats, were persons of interest in the investigation, India’s Ministry of External Affairs said in a statement on Monday. The ministry rejected what it called “preposterous imputations” made by Canada and said the move was politically motivated.