The undeclared shipment of Cuban weapons found on a North Korean ship are a violation of UN sanctions against arms transfers to Pyongyang, Panama said Wednesday, citing a UN report.

The public safety ministry said in a statement that according to a draft report by UN experts sent to Panama after the seizure of the ship in July, the cargo "undoubtedly violates UN sanctions, which supports the course of action Panama took."

The ministry statement was the first information released about the mission of the experts, who completed their inspections two weeks ago. They were led by Briton David Martin Uden, a former ambassador to South Korea.

A source in the public safety ministry said authorities had been given a first draft of the report compiled by UN sanctions panel experts.

North Korea is under UN sanctions over its controversial nuclear program which bar the transport of all weapons to and from the isolated state apart from the import of small arms.

Pyongyang carried out a third nuclear weapons test in February, triggering even tighter UN sanctions.

The ship, the Chong Chon Gang, was intercepted on July 10 as it tried to enter the Panama Canal on suspicion it was carrying drugs.

Authorities instead uncovered 25 containers of military hardware, including two Soviet era MiG-21 fighter jets, air defense systems, missiles and command and control vehicles.

Both Havana and Pyongyang said they were "obsolete" Cuban arms being shipped to North Korea for refurbishment under a legitimate contract.

The communist allies did not explain why the items were buried under more than 200,000 sacks of sugar inside the ship.

The United Nations has not stated publicly yet how it will proceed.

The ministry statement was released after a group of North Korean diplomats visited the ship's 35 crew members, who are being detained at a former military base on charges of arms trafficking.

The crew members face up to 12 years in prison if convicted.

Five percent of the world's commerce travels through the nearly century-old Panama Canal, with that expected to increase following the completion of a major expansion project. (AFP)