Canadian law enforcement officials said on Monday that the Indian government and its agents were running a broad criminal network in Canada, with a goal of intimidating and harassing Canadian Sikh separatists. The stunning accusations marked a grave new step in a dispute between the two nations that has been escalating for nearly two years.

A Canadian government official said that Canada had issued a persona non grata note on Monday morning to India’s High Commissioner to Canada Sanjay Kumar Verma, India’s top diplomat there, expelling him, along with a number of other diplomats, for their role in the alleged criminal activity, including extortion and homicide.

The Indian government, in a rival statement on Monday, said that it was pulling the diplomats out of the country, citing “an atmosphere of extremism and violence,” which it said endangered its diplomats’ safety in Canada.

The two countries have been in an intense dispute following the assassination of a Canadian Sikh cleric in British Columbia in June 2023, which the government of Prime Minister Justin Trudeau of Canada said at the time had been orchestrated by the Indian government.

Canada is home to a large Sikh community, and India has said that some Sikhs in Canada are actively involved in a secessionist movement that seeks to carve out a Sikh homeland, known as Khalistan.

The Indian government has vehemently denied the accusations that it was involved in the killing of the cleric and has claimed that Prime Minister Trudeau is pandering to Canada’s large Sikh community for political gain.

Hardeep Singh Nijjar, 45, a prominent Sikh leader and president of a Sikh temple in Surrey, British Columbia, was the cleric killed outside the temple last year. Three Indian nationals have been arrested and charged in the ongoing investigation.

The deepening rift between the two nations comes as the United States, the European Union and others try to court India as a counterweight to Russia on the world stage.

The breakdown in the already fraught relations between the two countries comes as a Canadian parliamentary committee is investigating the interference of foreign powers in domestic politics.

A Canadian parliamentary report in June, based on information provided by the country’s intelligence services, identified China and India as the two countries that pose the biggest risk of foreign interference in Canadian politics.

r. Kumar Verma has described the report as politically motivated and dismissed its findings. He is the equivalent of India’s ambassador to Canada.

Canada’s accusations against India regarding the assassination of Mr. Nijjar were bolstered by a United States investigation into a similar, unsuccessful plot against a U.S.-based Sikh cleric.

On Monday the Indian government expressed its full support for Mr. Kumar Verma. “The aspersions cast on him by the Government of Canada are ludicrous and deserve to be treated with contempt,” it said.

Anupreeta Das contributed reporting from New Delhi and Ian Austen from Ottawa.