Myanmar is working on a nuclear weapons programme, experts have concluded, after its existence was exposed by leaked photographs.
Intelligence monitoring of the country's arms purchases from North Korea has been intensified as a result.
Satellite tracking and electronic surveillance, in particular, have been stepped up.
Concerns over the regime's attempts to develop a nuclear bomb prompted the United States State Department to demand last week that the ruling junta disclose an inventory of its nuclear technology.
Secret documents and hundreds of photographs smuggled out of the country by a defector indicated that it was intent on developing nuclear weapons and long-range missiles.
Jane's Intelligence Review published a separate batch of photographs showing similar activities in buildings and behind security fences near the capital, Naypyidaw.
Fears that Myanmar had joined a clandestine nuclear network linking North Korea, Iran, Pakistan and Syria have been growing, but there has not been hard evidence until now.
Defector Sai Thein Win is an army major who trained as a defence engineer and missile expert.
He said he had access to two secret nuclear facilities, including a "nuclear battalion" north of Mandalay, "charged with building up a nuclear weapons capability".
Robert Kelley, an American former senior weapons inspector with the International Atomic Energy Agency (IAEA), said the evidence was the most compelling yet.
Intelligence agencies are seeking to provide the IAEA with proof of a clandestine programme in the hope of a formal inquiry. Regular shipments of rocket platforms and missile technology between North Korea and Burma, as well as other clandestine links, are under scrutiny.
Washington has told Myanmar's ruling generals that "they have international obligations we expect them to heed", a State Department official said. Myanmar has made clear its nuclear ambitions by agreeing terms with Russia for the sale of a light-water research reactor.
But the deal is on hold after the generals refused to update its "small quantities protocol" with the IAEA, which exempts it from regular inspections.