MIAMI —

Social media influencers Andrew and Tristan Tate appeared handcuffed and shackled in federal court Monday as their attorneys vowed to fight an extradition request from the United Kingdom on sex-crime charges, including rape and sex trafficking.

The brothers, who were arrested by US Marshals Saturday on their way to a bare-knuckle boxing event in Miami, remain in custody after the hearing.

The brothers were already facing rape and human trafficking charges in the UK over allegations from 2012 to 2015. New charges were brought Sunday after Bedfordshire Police investigated reports made by four additional victims, UK authorities said.

Attorneys for the brothers, who are dual US and UK citizens, asked for their release pending the outcome of the case.