The operation took place in the early hours of Wednesday, 2 September, after GNR officers noticed suspicious activity while carrying out coastal surveillance in the Arrábida Natural Park.

Officers suspected that illegal goods were being brought ashore by sea and launched an operation to prevent them from being collected and distributed.

Land and air units were brought into the area, allowing the authorities to monitor the unloading of the drugs near Albarquel.

One suspect was arrested during the operation.

The GNR said officers recovered 10 bales containing approximately 400 kilograms of cocaine, preventing the drugs from reaching the illegal market.

The operation was led by the GNR's Coastal and Border Control Unit, with support from the National Traffic Unit, Setúbal Territorial Command and the Maritime Police.

The GNR says it maintains permanent surveillance of Portugal's coastline and national waters as part of efforts to combat cross-border crime and the use of maritime routes for drug trafficking.

In a separate operation also announced on Wednesday, the GNR seized almost 4,000 litres of fuel in Trafaria, Almada, which authorities suspect was intended to provide logistical support for drug trafficking by sea.

Officers found 198 full fuel containers and two vehicles near the Trafaria dock. Several people fled when officers approached, while two high-speed boats seen near the fish market also left the area by sea.

The two incidents were announced separately by the GNR on the same day.