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 in recent days, according to officials.

Footage shows the police and navy surrounding the vessel before boarding, seizing the Class A substance and arresting four crew members, who are said to be from South America.

The suspects, including two Ecuadorians, a Venezuelan and a Colombian, were remanded in pre-trial custody after their court appearance in the Azores on Tuesday, said police.

Vítor Ananias, head of Portugal's police unit to combat drug trafficking, told a press conference that their different nationalities showed the organisation behind them was not just based in one country.

The Lisbon-based Maritime Analysis and Operations Centre (MAOC) said it had received information in recent days indicating that a criminal organisation was in the process of dispatching a submersible loaded with cocaine destined for Europe.

A few days later, a Portuguese ship successfully located the submersible approximately 1,000 nautical miles (1,852km) off the coast of Lisbon, in an operation backed by the UK's National Crime Agency and the US Drug Enforcement Administration.

Having seized the vessel, the navy said it could not be towed back to shore due to poor weather and its fragile construction, and it later sank in the open sea.

Vítor Ananias told reporters that "between the heat, the vessel's fumes and high waves, with difficult weather conditions, even one day is tricky [for the four men on board]. By the end of 15 or 20 days all you want is to get out".

Such incidents like these had been a "recurring situation in recent years", he added, in remarks quoted by Lusa news agency.

In March this year, a similar vessel carrying 6.5 tonnes of cocaine was seized about 1,200 nautical miles from Lisbon.

It also comes as the Trump administration ramps up its attacks on vessels it says are being used to smuggle drugs into the US.

Three men were killed last week in a US strike on an alleged drug vessel in the Caribbean, US Defence Secretary Pete Hegseth said on Sunday.

Experts have questioned the legality of such strikes under international law and they have drawn strong criticism from Latin American leaders whose citizens have been targeted.