OTTAWA (CP) - Canadian spies have been pondering one of the more chilling questions of the post-9/11 era: Does Osama bin Laden's al-Qaida have briefcase-sized nuclear weapons?

A newly obtained intelligence report examines the intriguing notion and concludes that whatever the answer, the terrorist network is intent on acquiring nuclear means. The assessment revives concerns that emerged as early as 1992 when Stanislav Lunev, a former Russian military intelligence officer, claimed his country's intelligence services had lost many of the portable, backpack-style devices, which weigh about 55 kilograms.

The June 2004 report, Al-Qaida Possessing Russian Nuclear Briefcases: Fiction or Fact?, was prepared by the national security threat assessment centre, a federal agency housed at the Canadian Security Intelligence Service.

A copy was recently obtained by The Canadian Press under the Access to Information Act.

The heavily censored document, portions of which remain secret, indicates the vexing question is being taken seriously by Canadian intelligence.

"Al-Qaida is interested in acquiring nuclear capabilities in order to expand its attack arsenal," the report says.

Earlier this year, Pakistani journalist Hamid Mir said al-Qaida may already possess portable nuclear weapons. He attributed the claim to a 2001 interview with bin Laden's second-in-command, Ayman Al-Zawahri, in which the al-Qaida figure said the group had purchased such bombs on the black market in central Asia for $30 million US.

The report notes that Russian officials and nuclear scientists have argued in the media it would be almost impossible for al-Qaida to posess such devices, as they are too difficult to maintain and have a lifespan of just one to three years.

Wesley Wark, a history professor at the University of Toronto, said the briefcases are unlikely to be in the hands of extremists.

"I think that there's great confidence that those kinds of weapons are accounted for and under control," he said.

"And that's not the kind of source that you would look to for a potential terrorist weapon," he added, saying they lurk "only in Hollywood imagination."

The report suggests a "dirty bomb" - which uses a conventional explosive to spread radioactive material - may be "a feasible alternative" to the Russian briefcase models.

"Except in the most extreme circumstances, it is unlikely that a radiological 'dirty bomb' would result in more casualties than could be achieved with a comparable conventional weapon," the assessment says.

"However, a contaminated area would pose long-term health concerns and could cause panic within the population."

Canadian intelligence has increasingly turned its attention in recent years to preventing industrial items from being diverted to the manufacture of illicit weapons.

The report notes the arrest of two men in Zambia last March who were suspected of possessing a cache of bomb-grade uranium, as well as the attempt by three men in May to sell highly radioactive cesium-137 in Ukraine.