Protesters carrying flags of the Jewish Defense League clashed with demonstrators outside the annual American Israel Public Affairs Committee gathering on Sunday.
The scuffle was caught in a Facebook video from the New York-based Jewish Voice website.
Some of the activity is off screen, but during the altercation one man, wearing the JDL insignia, beat another using a JDL flag as a bludgeon. A Palestinian flag was also thrown to the ground. The fight was ultimately broken up by police and bystanders.
A dozen JDL members or sympathizers also appeared in the video, confronting a much larger group of left-wing protestors who carried signs that read #JewishResistance.
Founded in 1968 by the firebrand Jewish nationalist Meir Kahane, the JDL is seeking to re-establish itself in the United States after decades of inactivity. Leaders of the nascent American branch can be seen in the same the video as well as the current head of the Canadian branch of the movement.