North Korea is calling for the release of 35 nationals who were arrested in Panama after authorities found Cuban-made missile materials hidden under tons of sugar.
North Korea's Foreign Ministry says Panama should release the crew because no drugs or illegal cargo were aboard.
A Foreign Ministry spokesman, who was not named by the official Korean Central News Agency, says "The Panamanian investigation authorities rashly attacked and detained the captain and crewmen of the ship on the plea of 'drug investigation' and searched its cargo but did not discover any drug."
Hidden under some 240,000 white sacks of raw brown Cuban sugar, Panamanian officials found shipping containers with parts of a radar system for a surface-to-air missile defense system, an apparent violation of U.N. sanctions that bar North Korea from importing sophisticated weapons or missiles.
Nearly 24 hours after Panama announced the find and said it would continue searching the ship for more contraband, Cuba acknowledged late Monday that the ship's cargo included 240 metric tons of "obsolete defensive weapons": two Volga and Pechora anti-aircraft missile systems, nine missiles "in parts and spares," two Mig-21 Bis and 15 engines for those airplanes. The equipment was meant to be repaired in North Korea and returned to Cuba, the Cuban government said.
North Korea said Wednesday "This cargo is nothing but aging weapons which (North Korea) are to send back to Cuba after overhauling them according to a legitimate contract."
"The Panamanian authorities should take a step to let the apprehended crewmen and ship leave without delay," the spokesman also said.
Cuba's explanation that sent the arms back to North Korea for repair is potentially credible but leaves troubling questions unresolved, international arms experts said Wednesday.
Acting on intelligence it hasn't publicly described, Panama seized the rusting, 34-year-old North Korean freighter Chong Chon Gang on July 11 as it headed toward the Caribbean entrance of the Panama Canal on its way to the Pacific and its final destination of North Korea.
The captain of the ship had a heart attack and also tried to commit suicide, said Panamanian President Ricardo Martinelli.
North Korea has a robust capability to repair and upgrade Soviet-era military equipment, and the economically struggling, isolated nation has a track record of trading technical help for commodities such as sugar, experts said.
At the same time, North Korea is known to be seeking to evade sanctions and get spare parts for its own weapons systems, particularly Mig jet fighters. That raises the possibility that in lieu of cash, Cuba was paying for the repairs with a mix of sugar and jet equipment, experts said.
"We think it is credible that they could be sending some of these system for repair and upgrade work," said Neil Ashdown, an analyst for IHS Jane's Intelligence. "But equally there is stuff in that shipment that could used in North Korea and not going back."
Britain's U.N. Ambassador Mark Lyall Grant said Wednesday that "any weapons transfers, for whatever reason, to North Korea would be a violation of the sanctions regime and therefore there are questions to be answered."
"If it is confirmed that the vessel was carrying arms and or related material and the shipment was part of a purchase or sale to or from the Democratic People's Republic of Korea, then that would indeed be a breach of the sanctions regime relating to that country," said U.N. spokesman Martin Nesirky. "But ... it's up to the sanctions committee of the Security Council to pronounce itself on that matter."
U.N. diplomats speaking on condition of anonymity because of the sensitivity of the issue said that if Cuba wanted to send the weapons for repairs and have them returned, they would need to get a waiver in advance from the Security Council committee monitoring sanctions against North Korea.
In 2010, the South African navy intercepted a shipment of upgraded tank engines that were being transported from North Korea to Congo-Brazzaville, said Hugh Griffiths, arms trafficking expert at the Stockholm International Peace Research Institute.
"The North Koreans have a track record of actually doing this," he said. "Upgrading, servicing and repairing, that's what the North Koreans do."
He said the deals are part of a barter trade, where North Korea upgrades military equipment in return for commodities, like Cuban sugar or, in another documented exampled, Burmese rice.
"It looks like it was definitely a violation of the U.N. sanctions, and this is why there was an effort to camouflage and conceal it," Griffiths said. "It is military equipment prohibited under U.N. sanctions so whether payment is made in the form of barter trade or foreign currency it still constitutes a violation."
Soviet-built air-defense missiles, radar systems and MiG-21 fighter jets are complex enough to periodically require a factory repair in addition to regular maintenance.
North Korea has developed arms industries producing missiles and other weapons derived from old Soviet designs and has found customers in countries that can't afford more expensive modern arms.
Cuba wouldn't be unique in sending its weapons for repairs abroad. In June 2012, a Russian-operated ship carrying three Soviet-built Syrian helicopters after repairs in Russia was forced to turn back after a British insurer removed its coverage.
Alongside the repair and upgrade business for countries with less advanced militaries, North Korea also has a long history of aggressively buying, marketing and selling entire weapons systems around the world, especially in developing countries in the Middle East, Africa and Southeast Asia.
Much of that business was in sales of short- and medium-range missiles, but the market for full missile systems is thought to have dried up in recent years.
That's partly because of international pressure and sanctions banning weapons exports that followed North Korea's three nuclear tests conducted since 2006 and a string of long-range rocket launches. Sales may have also suffered because of the poor-quality, Soviet-type weaponry that Pyongyang has traditionally produced.
Panamanian authorities said it might take a week to search the ship, since so far they have only examined one of its five container sections. They have requested help from United Nations inspectors, along with Colombia and Britain, said Javier Carballo, Panama's top narcotics prosecutor.
Photos of the ship's cargo show a green tube that appears to be a horizontal antenna for the SNR-75 "Fan Song" radar, which is used to guide missiles fired by the SA-2 air-defense system found in former Warsaw Pact and Soviet-allied nations, Ashdown said.
"The agreements subscribed by Cuba in this field are supported by the need to maintain our defensive capacity in order to preserve national sovereignty," Cuba's Tuesday statement read.
It concluded by saying that Havana remains "unwavering" in its commitment to international law, peace and nuclear disarmament.
Under current sanctions, all U.N. member states are prohibited from directly or indirectly supplying, selling or transferring all arms, missiles or missile systems and the equipment and technology to make them to North Korea, with the exception of small arms and light weapons.
The most recent resolution, approved in March after Pyongyang's latest nuclear test, authorizes all countries to inspect cargo inside or transiting through their territory that originated in North Korea. It also lets countries inspect cargo destined for North Korea if a state has credible information the cargo could violate Security Council resolutions.
In early July, a top North Korean general, Kim Kyok Sik, visited Cuba and met with his island counterparts.
The Chong Chon Gang has a history of being detained on suspicion of trafficking drugs and ammunition, Griffiths said. Lloyd's List Intelligence said the 34-year-old ship, which is registered to the Pyongyang-based Chongchongang Shipping Company, "has a long history of detentions for safety deficiencies and other undeclared reasons."
The Associated Press contributed to this report.