WASHINGTON — The F.B.I. arrested the leader of a violent California neo-Nazi gang on a federal conspiracy charge after he fled the country earlier this month.

Robert Rundo, 28, of Huntington Beach, Calif., is being held at the federal jail in downtown Los Angeles. He was charged in a criminal complaint that was unsealed Tuesday.

Mr. Rundo apparently crossed into Mexico two weeks ago from California and then made his way to Central America. He was later brought back to the United States, where he was arrested Sunday at Los Angeles International Airport, according to two people familiar with the case who spoke on the condition of anonymity because they were not authorized to speak publicly.

He is the founder of the Rise Above Movement, a neo-Nazi gang based in Southern California whose members were involved in violent activity at protests throughout California in 2017. He and three other Californians associated with the group — Robert Boman, 25, Tyler Laube, 22, and Aaron Eason, 38 — were charged with inciting riots, according to court documents. Mr. Boman and Mr. Laube were arrested on Tuesday morning in Southern California. The F.B.I. said it was still searching for Mr. Eason.