India said on Monday it was withdrawing its envoy to Canada because Ottawa was investigating him and other diplomats as “persons of interest”, after the killing last year of a Sikh separatist leader.

The 2023 murder of Canadian citizen Hardeep Singh Nijjar crashed diplomatic relations with India after Prime Minister Justin Trudeau said there were “credible allegations” linking Indian intelligence to the crime.

The withdrawal of India’s ambassador is a major escalation in the fraught ties between the nations.

“We have no faith in the current Canadian government’s commitment to ensure their security,” New Delhi’s foreign ministry said in a statement.

“Therefore, the government of India has decided to withdraw the high commissioner and other targeted diplomats and officials.”

India’s foreign ministry had earlier said in a statement it had “received a diplomatic communication from Canada suggesting that the Indian high commissioner and other diplomats are persons of interest” in the ongoing investigation.

It said their envoy, Sanjay Kumar Verma, a former ambassador to Japan and Sudan, was a respected career diplomat and that accusations against him were “ludicrous and deserve to be treated with contempt”.

Nijjar — who immigrated to Canada in 1997 and became a citizen in 2015 — had advocated for a separate Sikh state, known as Khalistan, carved out of India.

He had been wanted by Indian authorities for alleged terrorism and conspiracy to commit murder.

Four Indian nationals have been arrested in connection with Nijjar’s murder, which took place in the parking lot of a Sikh temple in Vancouver in June 2023.

India on Monday called allegations it was connected to the killing as “preposterous” and a “strategy of smearing India for political gains”.

Last year it briefly curbed visas for Canadians and forced Ottawa to withdraw diplomats, and on Monday threatened further action.

“India now reserves the right to take further steps in response to these latest efforts of the Canadian government to concoct allegations against Indian diplomats,” the foreign ministry said.

It said in a later statement it had summoned Canada’s charge d’affaires to the foreign ministry.

“Canada has provided credible, irrefutable evidence of ties between agents of the government of India and the murder of a Canadian citizen on Canadian soil,” said Canadian Charge d’Affaires Stewart Wheeler, speaking to reporters after leaving the ministry.

“Now, it is time for India to live up to what it said it would do and look into all those allegations. It is in the interest of both our countries and the people of our countries to get to the bottom of this. Canada stands ready to cooperate with India.”

Canada is home to some 770,000 Sikhs, who make up about two per cent of the country’s population, with a vocal minority calling for an independent state of Khalistan.

In November 2023, the US Justice Department also charged an Indian citizen living in the Czech Republic with allegedly plotting a similar assassination attempt on US soil.

Prosecutors said in unsealed court documents that an Indian government official was also involved in the planning.