Belgian police on Wednesday detained 30 suspects accused of drug trafficking in an operation that also saw authorities in Spain swoop on a string of locations.

Prosecutors in the port city of Antwerp, a major hub for illicit drugs coming into Europe, said in a statement that police conducted raids at addresses across Belgium.

It said Spanish police had simultaneously carried out seven searches in their country, but there were no details on any arrests there.

The raids in the two countries together netted guns, 55,000 euros (US$60,000) in cash, hauls of hashish and cocaine, luxury watches and cars, it said.

The police operation started a year ago with the surveillance of a restaurant in Antwerp frequented by Albanian nationals suspected of selling drugs.

Those trailed were in contact with a Spanish national resident in Brussels who investigators said was running an international trafficking operation.

The raids in southern Spain targeted relatives of this man.

The prosecutors said the man was suspected to have used "corrupt dock workers" in Antwerp to move hashish and cocaine through the port. (AFP)