An Algerian held in Italy as part of a probe into fake ID documents used by the Paris and Brussels attackers was interrogated on Sunday but refused to answer questions, a judicial source said.

The suspect, named as Djamal Eddine Ouali, 40, was detained under a European arrest warrant near the southern city of Salerno on Saturday, and questioned in prison by prosecutors, the judge in charge of the preliminary inquiry said.

Salerno police chief Alfredo Anzalone said he was confident Ouali's extradition to Belgium would be approved. A hearing on the matter is scheduled for Friday.

Ouali was held on Saturday evening at a bus stop in a joint swoop involving anti-terrorism officers and a police special operations unit in the town of Bellizzi, an area with a large population of transient seasonal workers, many from North Africa.

Belgium had issued a European arrest warrant for Ouali as it probes the false papers used by the Islamic State network that organised Tuesday's Brussels attacks, which killed 31 people, and November's assault on Paris that left 130 dead.

He is suspected of being part of a criminal network that produced fake documents for illegal immigration.

Suspicions were raised after local immigration officials checked Ouali's residency permit. Police had been searching for a man with the same name and belonging to the same organisation since January 6.

Hundreds of digital photographs were then seized from a counterfeiter's workshop, including three of those who planned the deadly attacks in Paris in November.

One of those photographed was Najim Laachraoui, a suicide bomber at Brussels airport, reports quoted police as saying.

Investigations are ongoing as to how Ouali came to be in Italy and into the networks of which he may have been a part.