Three men who were robbing a medical student in Sydney fled in panic when five members of a nearby martial arts school rushed to the rescue dressed in full ninja gear.
The trio attacked the 27-year-old German after he got off a train, New South Wales state police said.
As the assault was under way, a student coming out of class at the Ninja Senshi Ryu school saw what was happening and called on his teacher and three other students for help.
"We started running towards them and they took off. They would have seen five of us in ninja gear ... all in black with our belts on, running toward them," ninja sensei Kaylan Soto said. "I think they're probably still running if I'm not mistaken."
The victim suffered minor injuries, and the men stole his mobile phone and iPod, police said.
Police said that they had arrested a 16-year-old and 20-year-old and charged them with robbery. They are still seeking a third suspect.