Italy launched a major international police operation against the 'Ndrangheta organised crime group Wednesday, involving law enforcement officials in Germany, Romania and Spain, prosecutors announced.

It targeted two alleged clans of the mafia group, the Agresta and the Giorgi families, both from the 'Ndrangheta stronghold of Calabria in southern Italy.

It focused on international drug trafficking, notably in Piedmont in northern Italy, Calabria, Sardinia and in Germany, in Baden-Wurttemberg, anti-mafia investigators announced in a statement.

The operation was coordinated by prosecutors in Turin, northern Italy, and involved hundreds of officers across the four countries.

Assets worth "many millions of euros" were also being seized in the operation, the statement said, adding that further details would be unveiled later in the day.

The 'Ndrangheta, rooted in the southern region of Calabria, has surpassed Sicily's more famous Cosa Nostra to become Italy's most powerful mafia group, with tentacles in countries worldwide.

Its presence in Germany was highlighted in a massacre outside a pizzeria in the town of Duisburg in 2007.

Six rival clan members were killed as part of a long-running feud between families from the town of Calabria's San Luca - home to the Giorgi family.