ROME — The Italian police on Thursday arrested more than 330 people, including politicians, lawyers, accountants and a local police chief, in one of the most extensive law enforcement operations ever against the crime syndicate known as ’Ndrangheta.

About 3,000 officers made pre-dawn arrests in 12 Italian regions, as well as in Switzerland, Germany and Bulgaria, officials said. ’Ndrangheta has spread far beyond its historic base in the southern region of Calabria, surpassing the Cosa Nostra, based in Sicily, to become Italy’s most powerful mafia group. The group controls much of Europe’s cocaine trade, European officials say.

Nicola Gratteri, the anti-mafia prosecutor who coordinated the operation, described Thursday’s crackdown as “the biggest operation after the Palermo maxi trial,” a reference to a sweep in 1984 that led to a landmark trial against some 450 Sicilian mafia members. That case severely weakened the Cosa Nostra, but its decline permitted the Calabrian syndicate to grow more powerful.

Thursday’s operation “completely dismembered the top ranks of the Mancuso family,” the long-established ’Ndrangheta clan operating in the city of Vibo Valentia, with links to the United States, Mr. Gratteri said.