Image caption Mr Soto with his ninja trainees saved Sydney mugging victim

Three muggers in Australia got the fright of their lives when their attack was interrupted by five black-clad ninja warriors.

The thieves were assaulting a German medical exchange student in Sydney, but the alleyway where they struck was next to a school for ninja warriors.

One of the pupils raised the alarm after noticing the attack.

Police say they have arrested two men and charged them with robbery, and are still looking for a third suspect.

"We just ran outside and started running at them, yelling and everything," said ninja master Kaylan Soto who instructed his students to take action.

"These guys have turned around and seen five ninjas in black ninja uniforms running towards them. They just bolted."

The victim suffered minor injuries, and the men stole his mobile phone and iPod, according to police.

Mr Soto said the man could have escaped the assault with some training in ninjitsu - a Japanese martial art. As for the attackers, "They just picked the wrong spot," he added.