India says it has withdrawn its high commissioner to Canada after it said he and other diplomats were named as “persons of interest” in the murder investigation of a Sikh separatist.

India said it received the news in a diplomatic communication from Canada on Sunday, and reserved the right to respond, stressing it “strongly rejects these preposterous imputations”.

The statement refers to allegations last year by Canadian Prime Minister Justin Trudeau that India’s government may have been behind the killing on Canadian soil, an allegation Delhi rejects.

The row led to a deterioration in ties, with India asking Canada to withdraw dozens of its diplomatic staff and suspending visa services.

On Monday, a furious statement from India’s foreign ministry said Canada’s allegations were part of Trudeau’s “political agenda” and warned of action, without specifying what it would be.

“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,” it said.

Delhi also defended its High Commissioner Sanjay Kumar Verma, referring to his “distinguished career spanning 36 years”.

“The aspersions cast on him by the government of Canada are ludicrous and deserve to be treated with contempt,” it said.

There was no immediate Canadian response to Delhi’s statement. The country’s deputy head of mission in Delhi, Stuart Wheeler, was summoned by India’s External Affairs Ministry to explain Canada’s move.

“He was informed that the baseless targeting of the Indian high commissioner and other diplomats and officials in Canada was completely unacceptable,” a ministry statement said.

“We have no faith in the current Canadian government’s commitment to ensure their security. Therefore, the government of India has decided to withdraw the High Commissioner and other targeted diplomats and officials.”

Hardeep Singh Nijjar was shot and killed in June 2023 by two masked gunmen outside a Sikh temple he led in Surrey, British Columbia.

He had been a vocal supporter of the Khalistan movement, which demands a separate Sikh homeland, and publicly campaigned for it.

India has in the past described him as a terrorist who led a militant separatist group – accusations his supporters called unfounded.

Canadian police called his killing a “targeted attack”.

In September 2023, Trudeau had told Canada’s parliament that allegations of Indian involvement in the killing were based on Canadian intelligence.

He called the act a violation of Canada’s sovereignty.

India has vehemently denied all allegations and maintained that Canada has provided no evidence to support its claims.

Frosty ties between the two countries seemed to have thawed slightly after India resumed processing visas in October 2023.

But last week, Canadian Foreign Minister Mélanie Joly called the country’s relations with India “tense” and “very difficult”.

She also said there remained a threat of more killings like Nijjar’s on Canadian soil.