The father of a boy who was beaten by a masked gang in Londonderry has said the men threatened to shoot him if he intervened.

The 15-year-old boy was attacked in front of his father and has been treated in hospital after four men set upon him with hammers.

The father had a gun pointed at him throughout the ordeal, which took place in the Mimosa Court area of Londonderry.

He told the BBC: "I heard him shouting, I looked around and there were three or four boys beating him with masks on."

"I went toward the gate and a man pointed the gun at me and said, 'Stay where you are or you'll get it'.

"I knew the best thing to do was to stand back.

"If they knew I was there they were going to get off him faster and get away and then, at least, then I could help him.

"He was shouting, 'Help me, help me'. I know if it was me, it would scare me so what's it going to do to a child?"

A police spokesman said anyone with information about the incident is asked to contact Strand Road police station on 0845 600 8000 or speak to Crimestoppers anonymously on 0800 555 111.