Canadian police reported on Saturday that a fourth individual has been detained and accused in connection with the murder of Sikh separatist leader Hardeep Singh Nijjar last year. The matter has complicated diplomatic ties with India, according to Reuters.

Three Indian men were detained and charged by Canadian police earlier this month in the city of Edmonton, Alberta, and it was announced that the men were being investigated for possible ties to the Indian government.

In connection with the assassination of Nijjar, Amandeep Singh, 22, has been charged with first-degree murder and conspiracy to commit murder, according to a statement made on Saturday by the Integrated Homicide Investigation Team (IHIT).

The Indian national, Singh, was already detained for unrelated firearms charges out of Peel, Ontario. Singh lived in Brampton, Surrey, and Abbotsford, according to IHIT.

Najjar, 45, was shot and killed in June in Surrey, a suburb of Vancouver with a sizable Sikh community, outside a Sikh temple. A diplomatic crisis with New Delhi occurred a few months later when Canadian Prime Minister Justin Trudeau cited what he claimed to be proof of possible Indian government participation.

Najjar was a Canadian national who campaigned for the separation of India into an independent Sikh nation called Khalistan. Nijjar's classification as a "terrorist" was applied by New Delhi, which has long been upset by the existence of Sikh separatist groups in Canada.