Cape Verdean and US police have intercepted more than five tonnes of cocaine from a fishing boat and arrested seven people, in one of the Atlantic archipelago's largest drug seizures, local law enforcers say.

"The operation took place on April 1, after an approach on the high seas on suspicions of international drug trafficking," Cape Verde police chief Ricardo Goncalves told reporters on Wednesday evening.

"Under the jurisdiction of the Cape Verdean authorities, US and Cape Verde police boarded, inspected the fishing boat and went on to seize 5,668 kilos (12,496 pounds) of cocaine."

Police arrested five Brazilians and two Montenegrins. The fishing boat was travelling from Brazil.

As well as Cape Verdean forces, the operation involved US anti-drug services, the US navy, Brazil's federal police and the UK National Crime Agency, Goncalves added.

West Africa's coast is a major transit zone for cocaine smuggled from Latin America to Europe. 

Cape Verde's geography makes the Portuguese-speaking archipelago particularly vulnerable due to the vast body of water it must patrol with limited resources.

In January 2019, 9,570 kilos of cocaine were discovered in the port of the capital Praia on a Panama-flagged vessel travelling from South America to Morocco with a Russian crew.