India, June 24 -- In a landmark ruling that signals a hardening stance against political violence, a US federal judge has sentenced the leader of a self-styled militant cell, Antifa, to 100 years in prison for his role in a violent ambush at a Texas immigration detention centre.

Benjamin Song, a former US Marine Corps reservist, received the maximum sentence Tuesday for the attempted murder of a police officer, a penalty that marks the culmination of the first federal trial to successfully brand a group's actions as "antifa-inspired domestic terrorism."

The sentences handed down by US District Judges Mark Pittman and Reed O'Connor bring a definitive, if controversial, end to the aftermath of a July 4 incident last year, outside the Prai...