Ottawa/IBNS: Canadian authorities Saturday arrested a fourth Indian national for his suspected role in the murder of separatist leader Khalistan Hardeep Singh Nijjar, media reports said.

Twenty-two-year-old Amardeep Singh, a resident of Brampton, has been charged with first-degree murder and conspiracy to commit murder.

According to the Integrated Homicide Investigation Team (IHIT), Amardeep Singh was arrested on May 11 for his role in the killing of Hardeep Singh Nijjar.

He was already in the custody of the Peel Regional Police for unrelated firearms charges, said reports.

Earlier, the Canadian Police had arrested three in connection with the killing of Khalistani terrorist Hardeep Singh Nijjar in British Columbia last year.

The three accused arrested earlier were identified as Karan Brar, Kamalpreet Singh and Karanpreet Singh. The trio was charged with first-degree murder and conspiracy to commit murder in relation to the homicide.

The murder of the Khalistani leader had triggered a diplomatic row between India and Canada.

Nijjar, 45, was shot dead in June last year outside a gurdwara in Surrey, a Vancouver suburb with a large Sikh population.

A few months later, Canadian Prime Minister Justin Trudeau alleged Indian government involvement, triggering a diplomatic crisis with New Delhi.