Amsterdam - Italian national Giuseppe Nirta, aged 35, will remain in custody in the Netherlands until an Amsterdam court has decided whether or not he will be extradited to Italy to serve a prison sentence of 14 years and 18 months for dealing in drugs.
The leader of the so-called 'Ndrangheta clan from Italy is also a suspect for the German police in the gangland-style massacre.
In August 2007, a total of six Italians were murdered in Duisburg.
Wim de Bruin, spokesman of the Dutch public prosecutor, told Deutsche Presse-Agentur dpa on Tuesday that Italy had filed its request for the Nirta's arrest last month.