A timeline of Canada-India tensions - from 2018 to today's arrests

Relations between Canada and India have been under pressure for years, as Prime Minister Justin Trudeau and Indian Prime Minister Narendra Modi have quarreled over Sikh separatist elements in this country.

Canada is home to the largest Sikh community out‐ side of India - about 770,000 people, or about 2.1 per cent of the country's population, according to federal data.

Some of those Sikh Cana‐ dians (experts suggest they make up a relatively small share of the whole) support the creation of a separate Sikh homeland independent from India. They have sent money and resources to sup‐ port the cause and have staged unofficial referen‐ dums here in Canada, actions that have been condemned by India's leadership.

Trudeau, like his prede‐ cessors, has said Canada supports a "united India."

He hasn't cracked down on Sikh separatist discourse, despite intense Indian pres‐ sure to do so. Some Sikh Canadians have defended the push for an independent "Khalistan" as a peaceful movement for greater Sikh autonomy in India.

The fractious relationship came to a head last fall when Trudeau said publicly that Canadian authorities have been "actively pursuing credi‐ ble allegations of a potential link" between agents working for the Indian government and the murder of Sikh sepa‐ ratist Hardeep Singh Nijjar outside his Surrey, B.C. gurd‐ wara in June 2023.

India rejected Trudeau's claim as "absurd" and ac‐ cused Canadians of interfer‐ ing in "internal matters." Both countries subsequently kicked out each other's diplo‐ mats.

On Friday, Canadian police arrested members of a hit squad alleged to have car‐ ried out the Nijjar killing. In‐ vestigators have said they be‐ lieve the alleged assassins were retained by the Indian government.

Speaking to Punjabi media in Canada on the Sun‐ day before those arrests, Trudeau said the Nijjar inves‐ tigation will reveal some "very, very clear things that everyone around the world including in India - will see as to the responsibilities and in‐ volvement."

Here is a timeline of some of the events that have com‐ plicated Canada's bilateral re‐ lationship with India, the world's largest democracy.

February 2018

Prime Minister Justin Trudeau comes in for criti‐ cism after a troubled trip to India - a week-long visit meant to bolster relations with the world's largest democracy.

Trudeau had intended to use the trip to smooth over long-simmering tensions about support for Sikh sepa‐ ratism in the Canadian dias‐ pora, and to bolster Canada's relatively weak trading rela‐ tionship with India.

But the visit gets derailed when news emerges that Jas‐ pal Atwal, a B.C. man con‐ victed of attempting to mur‐ der an Indian politician in Canada, was invited by a Lib‐ eral MP to two functions at‐ tended by Trudeau.

The invitation, while not sanctioned by Trudeau, is a diplomatic embarrassment.

WATCH: Trudeau doing damage control on India trip

Trudeau and his family are also mocked for wearing traditional Indian garb during the visit, which attracts nega‐ tive scrutiny at home and abroad.

June 2023

Trudeau's national secu‐ rity adviser accuses India of being one of the top sources

of foreign interference in Canada, a public designation Ottawa had largely limited to authoritarian states up to that point.

In early June, India's for‐ eign minister, S. Jaishankar, criticizes Canada for allowing a float in a parade depicting the 1984 assassination of then-Indian Prime Minister Indira Gandhi by her body‐ guards. India sees the float as an effort to glorify vio‐ lence by Sikh separatists.

Two weeks later, on the evening of June 18, Sikh com‐ munity leader Hardeep Singh Nijjar is shot dead outside his gurdwara in Surrey, B.C. Con‐ gregants immediately call his killing a politically motivated attack.

WATCH: Crowds gather at the Guru Nanak Sikh Gurdwara in Surrey, B.C., after fatal shooting

Nijjar's death leads to heated protests against Indi‐ an officials throughout the summer.

The group Sikhs for Justice calls for people to "besiege" Indian consulates and offers cash rewards for the home addresses of Indian diplo‐ mats.

September 2023

In an unexpected move, Canada pauses talks on a proposed trade treaty with India. International Trade Minister Mary Ng also post‐ pones a mission to India, planned for October.

There is visible tension in New Delhi between Trudeau and Modi during the G20 leaders' summit.

A week later, on Sept. 18, Trudeau reveals that Canadi‐ an intelligence agencies are "pursuing credible allega‐ tions of a potential link" be‐ tween India's government and Nijjar's death.

WATCH: Canadians have a 'right to know' about alle‐ gations linking India to killing of Sikh leader: Trudeau

India subsequently re‐ stricts visas for Canadians ahead of the country's wed‐ ding season. It ultimately re‐ stores visa access in Novem‐ ber.

New Delhi says it had con‐ cerns about the safety of its diplomats in Canada, despite Indian High Commissioner Sanjay Kumar Verma saying weeks before that he had no such concerns.

India brands Canada a "safe haven for terrorists, ex‐ tremists" and "anti-India ac‐ tivities."

Sources tell CBC News the Canadian government had amassed both human and signals intelligence, including communications involving In‐ dian officials and Indian diplomats present in Canada, as part of the investigation into Nijjar's killing. Some of the intelligence was provided by an unnamed ally in the Five Eyes intelligence al‐ liance, according to the sources.

October 2023

India cancels diplomatic immunity for 41 Canadian diplomats, along with secu‐ rity protection for their rela‐ tives.

That effectively forces two-thirds of Canada's diplo‐ mats in the country to go home.

WATCH: India's move on diplomats 'contrary to in‐ ternational law,' PM says

Foreign Affairs Minister Mélanie Joly decries the move but pledges to hold further conversations with India in private.

November 2023

A New York court unseals an indictment alleging a foiled murder-for-hire plot led by an Indian diplomat against a Sikh separatist ear‐ lier that year.

WATCH: Indian PM makes first remarks about assassination plot claims

American officials allege the organizers behind the plot were pondering three other assassinations in Cana‐ da, including that of Nijjar.

January 2024

The independent inquiry into foreign interference in Canadian affairs asks Ottawa to share information about possible meddling by India in elections.

New Delhi rejects the sug‐ gestion it is behind any such acts and repeats its long‐ standing view that Canada al‐ lows Sikh separatists to inter‐ vene in its affairs.

March 2024

Bloomberg reports that the Indian government gave the U.S. a report which ac‐ knowledges that Indian agen‐ ts were involved in the U.S. murder plot, but claims they were rogue operatives.

Exclusive security video obtained by CBC's The Fifth Estate reveals the elements of the highly co-ordinated at‐ tack that ended with the killing of Nijjar.

WATCH: Surveillance video of the attack on Nij‐ jar

May 2024

CBC News reports that Canadian police have ar‐ rested members of an al‐ leged hit squad investigators believe was tasked by the government of India with killing Nijjar.