When Afghan refugee Abdul Aziz saw a man brandishing a gun outside his mosque in Christchurch, he ran towards the attacker armed with the only weapon he could find — a hand-held credit card machine.

Seven people were killed when a white supremacist stormed Linwood Masjid — the second mosque he attacked on Friday— as worshippers knelt to pray.

But the death toll could have been much higher if not for the heroic actions of Aziz, whose efforts to distract and chase the gunman away have attracted widespread praise.

"You don't have much time to think, whatever you think of, you just do it, you know," Aziz told AFP, brushing off the "hero" tag as local Muslims gathered to thank him for saving relatives and friends.

Aziz and his four sons were worshipping at the mosque when they heard the loud cracks of a gun being fired outside the building.

Initially thinking someone was setting off firecrackers, Aziz became suspicious and ran out of the mosque, grabbing a small credit card processing device.

Outside, he was stunned to find an armed man wearing military-style fatigues.

"At first, I didn't know if he was the good guy or the bad guy. But when he started swearing, I knew he was not the good guy," he said.

Aziz hurled the machine at Tarrant and then ducked between several cars as the self-confessed fascist unleashed a barrage of shots at him.

Aziz then heard one of his sons call out, "Daddy, please come back inside!"

Unhurt, Aziz picked up an empty shotgun that the gunman had discarded and shouted "come on here" repeatedly in an effort to draw him away from his sons and the other worshippers.

"When he see the gun in my hands, I don't know what happened, he dropped the gun and I chased him with my own gun ... I managed to throw the gun on his car and smash the car window, and I could see he was a bit frightened."

Aziz kept chasing the attacker as he sped off in his car.

The 48-year-old then returned to the mosque where he was greeted by scenes of carnage.

Aziz, an Australian, moved Down Under as a child refugee. He lived in Sydney for almost three decades before moving to Christchurch a few years later.

He says he has nothing but contempt for the attacker.

"A lot of people tell him he is a gunman. But ... a man never hurts anybody. He is not a man; he is a coward," Aziz said.