A preliminary report by a team of United Nations experts has determined that a North Korean cargo ship seized in Panama for carrying weapons violated sanctions, the Panamanian government has said.

A security ministry statement said the Cuban weapons found under sacks of sugar, including equipment for launching missiles, "without a doubt" violated sanctions meant to halt sophisticated arms sales to North Korea.

The ministry did not give further details and no one at the ministry answered phone calls from the Associated Press seeking comment.

The statement comes a day after the Stockholm International Peace Research Institute gave a similar assessment that it said was based on photographs and reports from Panamanian and UN authorities.

A UN panel of experts monitoring sanctions against North Korea visited Panama in mid-August to investigate the arms seizure. Its report has yet to be made public.

After the seizure Cuba said the cargo included "obsolete defensive weapons" including two MiG-21 jet aircraft and 15 motors, nine missiles in parts and two anti-aircraft systems that were being shipped to North Korea "to be repaired and returned".

North Korea said it had a "legitimate contract" to overhaul "ageing weapons" to be sent back to Cuba.

UN sanctions state that member states must prevent the direct or indirect supply, sale or transfer of all arms and materiel to North Korea, and related spare parts, except for small arms and light weapons.

The panel of experts could recommend the security council add individuals or entities involved in the transfer to a UN sanctions list. Member states could then decide to follow up by imposing travel and financial restrictions on those added to the list.