Leaders of 13 factions kicked out of the "Yamaguchi-gumi" syndicate - Japan's largest mobster or "yakuza" group which boasts 23,000 members and associates - held the first formal meeting in the western city of Kobe yesterday, local media reported.
One of the expelled factions is known as the Yamaken- gumi, which has about 2,000 members and whose head was chosen to lead the spin-off, according to the Yomiuri Shimbun newspaper.
Like the Italian Mafia and Chinese triads, the yakuza engage in everything from gambling, drugs and prostitution to loan sharking, protection rackets and white-collar crime.
But unlike their foreign counterparts, they are not illegal and each of the designated groups have their own headquarters.
As fears rise that the split could lead to a wave of gang violence, Japanese police last week called for nationwide vigilance, holding an emergency meeting with special officers from the country's 47 prefectures.