Portuguese police and naval forces have intercepted a semi-submersible vessel carrying more than 1.7 tonnes of cocaine in the mid-Atlantic Ocean, arresting four people in a joint international anti-narcotics operation.

According to officials, the so-called “narco-sub” was bound for the Iberian Peninsula and was seized after being detected around 1,000 nautical miles (1,852 km) off the coast of Lisbon. The operation, coordinated by Portugal’s Maritime Analysis and Operations Centre (MAOC), was supported by the UK’s National Crime Agency (NCA) and the US Drug Enforcement Administration (DEA).

Portuguese authorities confirmed that four crew members — two Ecuadorians, one Venezuelan, and one Colombian — were detained and have been remanded in pre-trial custody following a court appearance in the Azores on Tuesday.

Vítor Ananias, head of Portugal’s police unit for combating drug trafficking, told reporters that the suspects’ diverse nationalities reflected a transnational criminal network rather than an operation based in a single country.

“Between the heat, the vessel’s fumes, and high waves with difficult weather conditions, even one day is tricky for the men on board,” Ananias said. “By the end of 15 or 20 days, all you want is to get out.”

After the vessel was intercepted, Portuguese naval officers boarded the submersible, seized the Class A narcotic cargo, and detained the crew. However, officials said the fragile construction of the vessel and adverse weather made it impossible to tow to port, causing it to sink in open waters shortly afterward.

Footage released by Portuguese authorities shows naval vessels encircling the submersible before the boarding operation.

Ananias noted that such incidents have become increasingly common in recent years, as traffickers attempt to evade law enforcement with semi-submersible vessels capable of long-range, low-visibility transport across the Atlantic.

Earlier this year, in March, another narco-sub was seized about 1,200 nautical miles from Lisbon, carrying more than 6.5 tonnes of cocaine.

The interception comes amid a wider international effort to disrupt maritime drug trafficking networks. The MAOC said it had received intelligence that a criminal organization was preparing to dispatch the submersible loaded with cocaine destined for Europe.

Meanwhile, the U.S. has intensified its own maritime anti-narcotics operations. Last week, three men were reportedly killed in a U.S. strike on an alleged drug vessel in the Caribbean, according to U.S. Defense Secretary Pete Hegseth. The move has sparked international controversy, with experts questioning its legality under international law and Latin American leaders condemning the targeting of their citizens.

The latest seizure highlights the persistent and evolving challenge of drug trafficking across the Atlantic. Portuguese officials said they remain committed to working with international partners to intercept such vessels and dismantle the transnational networks behind them. (ILKHA)