Police backed by Portuguese navy and air force units located and intercepted a 24-meter (79-foot) yacht at sea, a statement said. They boarded it and found 183 bales of cocaine on board.
Police suspect the cocaine belonged to an international drug-trafficking gang that was bringing cocaine into Europe through the Iberian Peninsula.
Three men were arrested and taken to Portugal.
The operation involved police from Portugal, Spain, the U.S. Drug Enforcement Administration and the United Kingdom’s National Crime Agency.
Authorities said they would release further details of the operation later Monday.