US intelligence had been tracking the unflagged So San on its journey towards Yemen, officials said.

After the US said it might be carrying an illegal shipment, Spanish warships started to intercept it.

Warning shots were fired but the vessel, under a North Korean captain, refused requests to stop.

Helicopter-borne Spanish marines descended by rope onto the deck...

... and took control of the vessel in what the Spanish authorities are calling a brilliant operation.

None of the crew were injured as the vessel was intercepted.

Beneath cement sacks, a secret consignment of 15 Scud missiles was revealed .

MIssile parts, drums of chemicals and other, unidentified items were also uncovered.

North Korea's ballistic missile and nuclear programmes have caused deep concern to the US.