The United Arab Emirates claims to have seized a ship carrying banned weapons from North Korea bound for Iran, diplomatic sources said in New York.
The incident, which took place earlier this month, was apparently reported to the North Korea sanctions panel of the UN Security Council by the UAE.
South Korea's Yonhap news agency reported on Saturday that the panel was to meet soon to discuss the case.
The weapons, among them grenade launchers, had been listed as machine parts on the ship's manifesto, the report said.
Iran is one of North Korea's biggest weapons clients, making arms purchases worth about $2 billion annually, according to official US estimates.
The US and China are among the countries that last week reported having implemented Security Council sanctions against North Korea for continuing its prohibited nuclear activities.
In June, the council adopted a resolution to ban export of all weapons to and from North Korea as well as all financial transactions that could contribute to its nuclear weapons programme.
Resolution 1874 bans all 192 UN member states from engaging in arms dealing with the Stalinist state, and allows for the inspection of North Korean vessels if there is suspicion of arms trafficking.
The sanctions were imposed after Pyongyang conducted a nuclear test, its second, and test-fired several missiles earlier this year.
They aim at returning North Korea to the process of denuclearisation of the Korean Peninsula and meet previous commitments made in six-nation talks involving the US, Russia, China, Japan, and North and South Korea, whose goal is to dismantle Pyongyang's nuclear weapons programme.
In June, the US Navy shadowed a North Korean ship, believed to carry weapons destined for Myanmar, another pariah state, for two weeks, before the vessel returned to its home port without delivering its cargo.
The UAE seizure came at a time when North Korea was making a series of conciliatory gestures towards Seoul, following months of rising tension on the Korean Peninsula.