North Korea on Thursday demanded Panama to release without delay its ship and crew, seized after Cuban arms were found on board.

Havana said the weapons, which appeared to be a missile radar and other parts, were “obsolete” and were being sent to North Korea for repairs.

Pyongyang reinstated the claim in a statement by the foreign ministry, saying the shipment was part of a legitimate deal between the Communist nations.

“The cargo is nothing but ageing weapons which are to be sent back to Cuba after overhauling them according a legitimate contract,” the official Korean Central News Agency quoted the foreign ministry as saying.

“The Panamanian authorities should take a step to let the apprehended crewmen and ship leave without delay,” the ministry said.

It has also slammed Panama for “rashly attacking and detaining the captain and crewmen” of the Chong Chon Gang when they initially searched the vessel for drugs, reports Reuters.

Panama has urged UN inspectors to scrutinize the seized weapons found under tonnes of brown sugar, in what could be a possible breach of strict arms sanctions on North Korea.

“The cargo is illegal because it was not declared. Anything that is not logged, even if it is obsolete, is contraband,” Security Minister Jose Raul Mulino said.