Canada allowed the U.S. National Security Agency to conduct widespread surveillance during the 2010 Group of 20 summit in Toronto, according to a Canadian Broadcasting Corp report that cited documents from former NSA contractor Edward Snowden.

The report by CBC News late on Wednesday cited briefing notes it said showed the United States turned its Ottawa embassy into a security command post during a six-day spying operation by the top-secret U.S. agency as President Barack Obama and other world leaders met that June.

Reuters has not seen the documents and cannot verify their authenticity.

The report said the operation was no secret to Canadian authorities, with an NSA briefing note describing the operation as "closely coordinated with the Canadian partner."

The Canadian equivalent of the NSA is the Communications Security Establishment Canada, or CSEC.

The CBC report said the documents did not reveal the precise targets of the NSA operation, but described part of the U.S. eavesdropping agency's mandate at the Toronto summit as "providing support to policymakers".

A spokesman for Canadian Prime Minister Stephen Harper declined to comment on the allegations in the CBC report.

"We do not comment on operational matters related to national security. Our security organizations have independent oversight mechanisms to ensure that they fulfill their mandate in accordance with the law," Jason MacDonald said in an email to Reuters.

Harper came under fire from opposition politicians last month after a report by a Brazilian broadcaster alleged CSEC spied on a Brazilian government ministry. That report strained ties with Brazil.