Two Russian Embassy staff in Ottawa have left Canada in the wake of spying allegations against a Canadian naval officer in Halifax, but there's little else that's clear about the murky espionage case.

Intelligence experts and those in close contact with the embassy disagree on whether any Russian diplomats engage in spying, leaving Canadians to try to piece together what bits are public.

Initial media reports said up to four Russian Embassy staff had been removed from a list of embassy and diplomatic staff recognized by Canada. CBC News has confirmed that two have had their credentials revoked since news broke of the naval officer's arrest, while two diplomats left the country a month or more before the arrest this week of Canadian Sub.-Lt. Jeffrey Paul Delisle.

Another report pointed to two other staff who are no longer accredited to be in Canada. It's not clear which of the staff have been expelled over the spying allegations.

Konstantin Kolpakov, a former aide to the ambassador, was scheduled to leave Canada on Dec. 25 because his posting was over, and had a send-off attended by diplomats in Ottawa mid-month.

CBC News has also learned Lt.-Col. Dmitry V. Fedorchatenko, assistant defence attaché, was scheduled to leave in November.

Kolpakov and Fedorchatenko were known to circulate around the diplomatic scene in the capital, attending functions with other foreign representatives, Canadian diplomats and journalists.

Two others, Mikhail Nikiforov and Tatiana Steklova, were listed as administrative and technical staff until Jan. 19 but are no longer on a list of accredited diplomats on the website of the Department of Foreign Affairs.

Russia, Canada not commenting

A report in the Russian media Friday quoted the country's foreign ministry as saying it was surprised to see Canadian media reports about the expulsions. The report says the embassy staff left at the end of 2011 because their rotations were ending.

A woman who answered the phone at the Russian Embassy in Ottawa refused to comment on the departures.

Public Safety Minister Vic Toews refused to comment on a national security matter, but did say: "I'm not aware of why those individuals left Canada."

Lt.-Col. Kay Kuhlen, defence attaché for the German Embassy and head of the Ottawa Service Attachés Association, an organization that helps military diplomats, said he was advised in September that Fedorchatenko was leaving. His farewell event was Nov. 10. He also said he is "surprised" by the reports of spying.

Russian diplomatic staff usually do two- or three-year postings at the embassy before returning home or going on to a posting in another country.

Delisle, 40, was arrested in the Halifax area last weekend. He faces two charges under the Security of Information Act that deal with communicating information that could harm Canada's interests, according to court documents.

Canadian naval officer and Halifax native Jeffrey Paul Delisle, seen in this 1990 high school yearbook photo, is accused of passing defence secrets to the Russians.

'Everybody' in embassies collects information

Doug Thomas, a former defence official who now represents a Russian military equipment exporter in Canada, said the vast majority of diplomats collect information, while a small number may pick it up "through alternative means." Thomas doesn't believe anyone at the Russian Embassy, with whom he's worked since 2006, is involved in spying.

"If you were going to run one of these operations, the last thing, personally, I’d think you’d want to do is run it out of the Russian Embassy on Charlotte Street in downtown Ottawa. You’d want to run it remotely," he said.

But the Russians "are among the world’s biggest spies," said Wesley Wark, an expert on security and intelligence at the University of Ottawa. "Spying is just in the DNA of the Russian state."

Wark said the Russians are known to be aggressive, flooding their diplomatic missions with intelligence personnel posing as diplomatic personnel. He said the country, if it uses spying effectively, could close research and development gaps. They may also want access to Canadian communications with the U.S. and the U.K. or other allies.

"We [Canadians] tend to underrate ourselves as an intelligence target. We’ve long been an intelligence target, partly because of who we are. We’re a NATO country, we’re a Western country, we’re a high-tech country, we engage in a lot of military operations and we’re close to the United States and close allies," Wark said.

Geoffrey O'Brian, a former director general of counter-intelligence at the Canadian Security Intelligence Service, said there's so little information available that it's hard to assess the situation.

"Because the government has chosen not to talk about this, it's frankly in some ways a recipe for speculation," O'Brian said.

Many questions remain, particularly from a counter-espionage angle, O'Brian said.

"Are there more [people gathering information]? How was he recruited, if indeed he was? How was it run? Who else was involved in quote-unquote handling him? All of those questions."

Charges relate to security information act

Two of the charges against Delisle are for breach of trust and communicating to a foreign entity information the government wants to safeguard, and cover July 7, 2007, to Jan. 13, 2012. A third charge is for trying to communicate to a foreign entity information the government wants to safeguard, and covers Jan. 10 to 13, 2012, after at least one of the Russian diplomats left Canada.

Defence Minister Peter MacKay described the case Tuesday as a matter of national security because of the charges involved, but would not discuss specifics at that time, including whether the foreign entity in question was Russia.

"Given the early stages of the proceedings, there is really nothing more that can be said," he told a news conference in Ottawa.

The minister sought to reassure Canadians that allegations of espionage revolving around the Halifax naval intelligence officer would not affect the country's reputation among other NATO members.

"Our allies have full confidence in Canada, full confidence in our information," MacKay said.