The US Navy said on Sunday it seized an illicit shipment of weapons from a vessel in the Arabian Sea on May 6 and 7.
The guided-missile cruiser USS Monterey found the weapons on a "stateless dhow" in an operation that began Thursday in the northern reaches of the sea. A dhow is a traditional sailing ship popular in the Middle East.
“The cache of weapons included dozens of advanced Russian-made anti-tank guided missiles, thousands of Chinese Type 56 assault rifles, and hundreds of PKM machineguns, sniper rifles and rocket-propelled grenades launchers,” the navy said.
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Other weapon components included “advanced optical sights”.
The cargo was discovered “during a routine flag verification boarding conducted in international water in accordance with customary international law”, the navy said.
It did not identify where it believed the shipment originated.
“The original source and intended destination of the material is currently under investigation,” it said.
The materials are currently in US custody awaiting final disposition.
“After all illicit cargo was removed, the dhow was assessed for seaworthiness, and after questioning, its crew was provided food and water before being released.”
US and other allied forces in the region usually embark upon shipments of illegal weaponry that are suspected to be heading towards Yemen.
Yemen's internationally recognised government has repeatedly said that illegal arms had been smuggled into poorly controlled ports.
The country has endured a six-year conflict after the Houthi rebels ousted the government from the capital, Sanaa, in 2014, saying they were fighting a corrupt system and foreign meddling.
A Saudi Arabia-led military coalition intervened on behalf of the government the following year to restore its seat in Sanaa.
Since 2015, the UN Security Council has imposed an arms embargo on the Houthis. Despite that, UN experts say that “an increasing body of evidence suggests that individuals or entities in the Islamic Republic of Iran supply significant volumes of weapons and components to the Houthis”.
This latest seizure appeared to be among the biggest. Tim Michetti, an investigative researcher who studies the illicit weapon trade, told the Associated Press, the shipment bore similarities to the others.
"The unique blend of materiel recovered by the USS Monterey appears to be consistent with the materiel from previous interdictions, which have been linked to Iran," he said.