Four people have been detained after Portuguese authorities intercepted a narco-sub carrying more than 1.7 tonnes of cocaine in the mid-Atlantic.

The semi-submersible vessel was bound for the Iberian peninsula and was seized by the Portuguese Navy in recent days. Video released by authorities shows police and navy officers surrounding the vessel before boarding, seizing the Class A drugs, and arresting four crew members said to be from South America.

Police said the suspects, two Ecuadorians, a Venezuelan, and a Colombian, were remanded in pre-trial custody following a court appearance in the Azores on Tuesday.