Canada on Monday expelled a top Indian diplomat and said it was "actively pursuing credible allegations" linking Indian government agents to the murder of a Sikh separatist leader in British Columbia on June 18. Prime Minister Justin Trudeau said in Parliament that Canadian intelligence agencies have been looking into the allegations after Sikh leader Hardeep Singh Nijjar, a strong supporter of an independent Sikh homeland known as Khalistan, was gunned down on June 18 outside a Sikh cultural centre in Surrey, British Columbia.

Trudeau told Parliament that he brought up the slaying with Indian Prime Minister Narendra Modi at the G-20 last week. He said he told Modi that any Indian government involvement would be unacceptable and that he asked for cooperation in the investigation.

Meanwhile, let's take a look at who is Hardeep Singh Nijjar?

- Hardeep Singh Nijjar, who was shot dead on June 18 this year, was wanted in India with National Investigation Agency (NIA) having announced a cash reward on him.

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- The Khalistan Tiger Force chief was a native of alandhar's Bharsingh Pura village. He played an important role in organising the Khalistan referendum in Brampton. It was claimed that over one lakh people joined the activity.

- Nijjar was also included in the list of four people in whose name a chargesheet was filed by the NIA in connection with a conspiracy to kill Kamadleep Sharma, a Hindu priest in Jalandhar. The conspiracy was hatched by Arshdeep and Nijjar, both based in Canada, to disturb peace and disrupt communal harmony in Punjab by killing a Hindu priest, the Tribune quoted NIA as saying.

- According to a report by ANI, it is said that he was married with two sons and worked as a plumber.

- Nijjar used to work with Avtar Singh Khanda, a Khalistani leader of the Khalistan Liberation Force (KLF) who died due to cancer in the UK, a week earlier to Nijjar's death.

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- He was also the mastermind behind the assassination of self-claimed spiritual leader Baba Bhaniara in 2014.

- India has asked the Canadian authorities to take action against Hardeep Singh for his alleged involvement in terrorist activities in Punjab.