The North Korean vessel Chong Chong Gang at Manzanillo harbour in Colon, 90 km from Panama City on July 16, 2013. Panama's president Ricardo Martinelli said Monday that North Korean ship captain tried to kill himself after the vessel was stopped in route from Cuba and found to have suspected missile material on board. Photographer: Rodrigo Arangua/AFP via Getty Images
The North Korean vessel Chong Chong Gang at Manzanillo harbour in Colon, 90 km from Panama City on July 16, 2013. Panama's president Ricardo Martinelli said Monday that North Korean ship captain tried to kill himself after the vessel was stopped in route from Cuba and found to have suspected missile material on board. Photographer: Rodrigo Arangua/AFP via Getty Images

To paraphrase Ricky Ricardo, "Raul Castro, you got some 'splainin' to do!"

Panama's president, Ricardo Martinelli, revealed yesterday in a radio interview and in Twitter posts that Panama had found "sophisticated missile equipment" on a North Korean ship bound homeward from Cuba. Such shipments would be a clear violation of United Nations Security Council resolution 1718, adopted in 2006 after one of North Korea's three nuclear tests. It forbids the import from or export to North Korea of most weapons systems besides small arms.

The blurry pictures of the illicit cargo, contained under a shipment of brown sugar, speak only to the cognoscenti. The weapons mavens at IHS issued a report saying that the containers probably held the fire-control radar for the SA-2 family of surface-to-air missiles, and speculated that the cargo was either a sale to North Korea or a shipment that was being sent for upgrading, with the brown sugar as payment.

Full details on other parts of the cargo have yet to be released. The violent reaction of the crew and its captain -- who apparently tried to commit suicide -- suggest that the shipment was covert. If it does indeed violate UN sanctions, it is an ugly reminder of the real face of Cuba's leadership and its alliances with the world's worst malefactors. Although the Cubans and North Koreans have had a fitful, and occasionally bizarre, relationship over the years, just two weeks ago the chief of staff of North Korea's army visited Havana. He probably wasn't there for the cigars.

The Cubans should have their noses rubbed in this at the United Nations, at a minimum. And the Obama administration would be wise to demand an end to such transactions as an ironclad condition for any further improvement in relations.

More broadly, this inspection is a reminder of the need to get other countries to tighten enforcement, and reporting, on North Korean sanctions violations, as a UN panel has repeatedly recommended. The ship involved, the Chong Chon Gang, is a repeat offender: In January 2010, the Ukrainian government seized handguns, ammunition, narcotics and psychotropic substances and other contraband on board. In light of the most recent seizure, the Ukrainians' contention that the 2010 shipment didn't seem to involve North Korea's government rings as hollow as one of the Chong's bogus cargo containers.

(James Gibney is a member of the Bloomberg View editorial board. Follow him on Twitter.)