The International Boxing Association (IBA) has suspended federations from New Zealand, Germany, the Netherlands and Sweden for joining a "rogue" rival organization, it said on Monday.
A group including the United States and Britain announced the establishment of Swiss-registered World Boxing last month in a breakaway aimed at securing the troubled sport's Olympic future.
Its interim executive board features representatives from Germany, Britain, the Netherlands, New Zealand, the Philippines, Sweden and the United States.
USA Boxing, representing the most successful country in the sport's Olympic history, has terminated its IBA membership.
The IBA said New Zealand, Germany, the Netherlands and Sweden were suspended "due to their participation in a rogue boxing organization" but could be readmitted if the involvement ceased.
They must also publish a statement on their official websites "explicitly condemning any attempts to establish an alternative international boxing federation."
The IBA said the Czech federation was also suspended after organizing a tournament where USA Boxing fighters were allowed to take part.
Liberia and Equatorial Guinea were suspended for failing to provide annual reports.
Federations from Iceland and Ireland provided annual reports following the commencement of proceedings against them.
The IBA said boxers and officials from suspended national federations could still take part, with national flags and anthems but without federation symbols, in IBA-sanctioned competitions if registered directly through the IBA.
There was no immediate comment from World Boxing on how many countries have joined its organization.
Boxing's place in the Olympics after next year's Paris Games remains uncertain, with the sport not on the initial program for Los Angeles 2028, pending reforms demanded by the International Olympic Committee.
The IBA was suspended by the IOC in 2019 and stripped of involvement in the 2020 Tokyo Olympics and the qualifiers for Paris 2024.