Image caption Jeffrey Delisle had "coldly and rationally" offered his services to Russia in 2007, a judge said

A Canadian ex-navy intelligence officer has been jailed for 20 years after pleading guilty to selling classified Nato information to Russia.

Sub Lt Jeffrey Delisle, who was arrested in January last year, was also fined CA$111,000 (£70,000).

He admitted emailing secret files shared by Canada, the US and other Nato allies to Russia for four years.

Delisle is the first Canadian to be sentenced under the country's Security of Information Act.

The act was passed by parliament after the September 2001 attacks on the US.

Delisle was found guilty of giving classified information to "a foreign entity" between July 2007 and Jan 2012.

He had worked at top secret Canadian naval military facilities where he had clearance to intelligence-sharing systems linked to countries such as the US and UK.

For nearly four years he copied secret information on to memory sticks to share with his handlers in Moscow, in exchange for a monthly fee of $3,000.

'Professional suicide'

The 41-year-old had "coldly and rationally" committed treachery when he walked into the Russian embassy in Ottawa in 2007 to volunteer his spying services, judge Patrick Curran said during Friday's sentencing.

Prosecution witnesses said it was likely that Delisle put Canadian intelligence agents in danger, the BBC's Lee Carter reports from Toronto.

The case has become a major embarrassment for Canada as its military and government struggle to explain how the former navy officer was able to use such primitive methods to copy and convey his material and remain undetected for so long, our correspondent adds.

Observers said Delisle's guilty plea last October came as a surprise. It meant a publication ban was lifted, allowing details from the case to be published for the first time.

At a bail hearing in March last year, portions of a police statement were read out in which Delisle reportedly described the day he walked into the embassy as "professional suicide".

"The day I flipped sides... from that day on, that was the end of my days as Jeff Delisle," said the statement.

Suspicions were raised when Delisle returned in 2011 from a four-day trip to Brazil - where he had met a Russian handler - with several thousand dollars in cash.

That prompted the involvement of the Royal Canadian Mounted Police, who broke into an email account he shared with his handlers.

He reportedly worked for a unit that tracked vessels entering and exiting Canadian waters, with access to information shared by the Five Eyes community that includes Canada, the United States, Britain, Australia and New Zealand.

Canada's military has not revealed any details about any information disclosed to the Russians.