India suspended on Thursday the issuing of visas in Canada, the service provider said, amid a diplomatic row sparked by Ottawa's accusation New Delhi was involved in the killing of a Sikh separatist near Vancouver.

"Important notice from Indian Mission: Due to operational reasons, with effect from 21 September 2023, Indian visa services have been suspended till further notice," BLS International posted on their website on Thursday.

Canada's Prime Minister Justin Trudeau has demanded India treat with "utmost seriousness" allegations that Indian agents played a role in the June murder of Hardeep Singh Nijjar.

The fallout prompted tit-for-tat diplomatic expulsions and a forceful denial from India, which said any suggestion it played a role in Nijjar's killing was "absurd".

The suspension of visas comes a day after India's foreign ministry said it was concerned for the safety of its citizens in Canada because of "politically-condoned hate crimes and criminal violence".

"Threats have particularly targeted Indian diplomats and sections of the Indian community who oppose the anti-India agenda," a ministry statement said on Wednesday.

"Indian nationals are therefore advised to avoid travelling to regions and potential venues in Canada that have seen such incidents."

The advisory did not name specific cities or locations for Indians to avoid.

Nijjar was shot dead by two masked assailants outside the Sikh temple he presided over in Surrey, a city near Vancouver.

An activist for the creation of a Sikh state known as Khalistan, Nijjar was wanted by Indian authorities for alleged terrorism and conspiracy to commit murder.

The Indian government accuses Ottawa of turning a blind eye to the activities of radical Sikh nationalists who advocate the creation of an independent Sikh state to be carved out of northern India.