The 34-year-old victim, identified only as 'Said', says he was assaulted by three dark-clothed men in October while in a run-down Athens neighbourhood.
"I was walking on the street and talking on the phone when three men dressed in black attacked me. They hit me," the Iranian told the Greek branch of Doctors of the World in a video posted online.
"One of them put me in a headlock and severed my ear with his teeth," he added.
However, the trend abated after a Greek musician was fatally stabbed by a neo-Nazi supporter last year, prompting a crackdown that has put a third of the party's 18 lawmakers behind bars.
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Nikitas Kanakis, head of Greece's Doctors of the World branch, told AFP that the organisation had not publicised the Iranian's beating in October so as not to influence the investigation.