India said Tuesday it was willing to examine evidence presented by Canada alleging New Delhi's involvement in the killing of a Sikh separatist near Vancouver but repeated its criticism of Ottawa.

Relations between the two countries plunged last week as Prime Minister Justin Trudeau publicly linked Indian intelligence to the killing in June of Hardeep Singh Nijjar, a Canadian citizen who advocated a separate Sikh state carved out of India, and expelled an Indian diplomat.

India's top diplomat, asked during a visit to New York for the United Nations General Assembly whether India would review any evidence from Canada, said New Delhi would review information from any country.

"If there's any incident which is an issue and somebody gives me something specific as a government, I would of course look into it," External Affairs Minister Subrahmanyam Jaishankar said at the Council on Foreign Relations.

Canada has called for India to cooperate in the investigation but New Delhi has rejected the allegations and taken countermeasures, such as shutting down visa services for Canadians.

"We have actually been badgering the Canadians. We've given them loads of information about organized crime leadership which operates out of Canada," Jaishankar said, referring to Sikh separatists.

"Our concern is that it's really been very permissive because of political reasons," he said.

"We have a situation where actually our diplomats are threatened, our consulates have been attacked and often comments are made (that are) interference in our politics," he said.

Canada is home to some 770,000 Sikhs, or about two percent of the country's population, with a vocal group voicing support for creating a separate state of Khalistan.

The Sikh separatist movement is largely finished within India where security forces used deadly force to put down an insurgency in the 1980s.