The Duisburg murders highlighted the Calabrian Mafia's reach
Police in Amsterdam have arrested the main suspect in the gangland killing of six Italian men in the German city of Duisburg in August 2007.
Giovanni Strangio was detained with his brother-in-law - also a Mafia suspect - in a joint operation involving Dutch, German and Italian police.
Police believe the killings were part of a long-running feud among members of the Calabrian Mafia, the 'Ndrangheta.
The victims, linked to the Pelle-Votari clan, were gunned down near a pizzeria.
The killers are believed to be members of the rival Nirta-Strangio clan, based in the Italian town of San Luca.
Several other suspects have been arrested in Italy.
The Calabria-based 'Ndrangheta has become one of the most powerful criminal organisations in Italy, correspondents say, having overtaken the Sicilian Mafia, the Cosa Nostra, with the expansion of its international drug trafficking activities inside Europe.
For more than a decade, San Luca, a town of about 4,500 at the southern tip of Italy, has been the focal point of a bitter feud between rival 'Ndrangheta clans.
The feud dates back to an egg-throwing incident in 1991, when a fight broke out that left two young men dead and two injured.
The murder of Maria Strangio, a cousin of Giovanni Strangio, on 25 December 2006 is also believed to have been linked to the feud.