A ship from Cuba to North Korea, detained by Panama after it was found to hold undeclared military cargo, contained the fuselages of two Soviet-era fighter planes, UPI.com reported. The planes and other military items were hidden under bags of sugar and were being sent to North Korea for repairs, Cuba said on Monday.

Panama has recently asked the United Nations to investigate if the ship violated sanctions against North Korea prohibiting the supply of arms, news reports said. Investigators in Panama said they found anti-aircraft radars, which are capable of launching anti-aircraft weapons, in addition to the MiG-21 jets, news reports also said. They said evidence pointed to the MiGs having recently been flown.

"You are all here and are sensing the strong odor of fuel, to such a degree that no-one can know what danger Panama was put in," Panama Attorney General Ana Belfon said.

Seven containers were unloaded from the Chong Chon Gang so far, but officials said they expect to find more buried among the heavy quantities of of sugar.

Havana authorities admitted to shipping 240 tonnes of "obsolete" defensive weapons, including the jet fuselages, anti-aircraft missile complexes, nine missiles in parts and spares and 15 MiG engines, UPI.com reported.

UN sanctions experts plan to travel to Panama to inspect the shipment on August 5. Panama's President Ricardo Martinelli said the two jets, anti-aircraft missile batteries and other parts have been found on board.

"Apparently these aircraft were in use because they had fuel," President Martinelli said.

North Korea has insisted the shipment is entirely legitimate and demanded the release of the crew members.