Panama called Tuesday for UN investigators to inspect a shipment of suspected weapons parts aboard a North Korean-flagged ship as it tried to enter the Panama Canal last week.
President Martinelli tweeted a photo of the suspected weapons cache, which weapons experts have identified as an ageing Soviet-built radar control system for surface-to-air missiles.
The government said the contraband munitions were hidden under thousands of bags of sugar aboard the North Korean-flagged Chong Chon Gang.
Officials said if the shipment is indeed determined to contain missile components, that could violate a UN ban on most weapons being shipped into or out of North Korea.
Panama's Security Minister Jose Raul Mulino told RPC radio that the affair now is a matter for United Nations investigators.
"The Security Council will have to send experts," he said.
The United States hailed the Panamaian action, and said it stood ready to help if needed.
Asked if Washington was concerned Cuba was also implicated in possible arms smuggling to Pyongyang, State Department spokesman Patrick Ventrell said it was too early to say but added that "any country that would be exporting arms or arms-related material to North Korea would be in violation" of UN resolutions.
In the meantime, authorities here said they were continuing to unload thousands of bags of sugar that had concealed the suspected weapons shipment.
The magazine IHS Jane's Defence Weekly said Tuesday that the photo tweeted appeared to show an "RSN-75 'Fan Song' fire-control radar system."
The weapons were developed in 1957 and frequently used during the Vietnam War.
Officials in Panama said the crew resisted and the ship's captain attempted to commit suicide after the vessel was stopped as it prepared to enter the canal on Friday -- making the shipment even more suspicious, according to weapons experts.
"The manner in which the cargo was concealed and the reported reaction of the crew strongly suggests this was a covert shipment of equipment," Jane's Defence Weekly said in a statement.
Martinelli said the ship, which was sailing from Cuba with a crew of about three dozen, was targeted Friday by drug enforcement officials as it approached the Panama Canal and was taken into port.
After a search, officials found the contraband missiles hidden in a shipment of 220,000 pounds (100,000 kilograms) of sugar.
"The world needs to sit up and take note: you cannot go around shipping undeclared weapons of war through the Panama Canal," he told Radio Panama listeners on Monday.
The vessel was headed back to North Korea when it was stopped and taken to a port in Manzanillo, east of the Atlantic opening of the Panama Canal and is being held in a restricted zone, officials said.
Cuba is the only one-party Communist regime in the Americas, and a rare ally of also isolated Pyongyang.
Presidential spokesman Luis Eduardo Camacho said an examination of the ship by weapons specialists may take as long as a week.
North Korea defiantly carried out its third nuclear weapons test in February and then threatened to attack the United States, in language that was shrill even by its standards.
The North has for decades had a program to develop missiles of all types. Last December it successfully launched a three-stage rocket which placed a satellite in orbit.
Pyongyang said the operation was a peaceful scientific mission, but the launch was widely condemned as a covert ballistic missile test banned under United Nations resolutions.
It is unclear whether the North has the technology to build a nuclear warhead for a missile.
UN sanctions bar the transport of all weapons to or from North Korea apart from small arms. Several of the country's ships have been searched in recent years.
In July 2009 a North Korean ship heading to Myanmar, the Kang Nam 1, was followed by the US navy due to suspicions it was carrying weapons. It turned around and headed back home.
There has been, as yet, no reaction from Pyongyang or Havana over the quarantining of the ship, officials here said.
Five percent of the world's commerce travel through the century old Panama Canal, and that is expected to increase, posing challenges for policing it.