The child was walking with his family near the popular beauty spot the Giant's Causeway, when he and an older brother were caught by the wave and fell into the sea.

The older boy was rescued by the children's father and uncle, but an air and sea rescue operation did not locate the younger child for an hour.

Three lifeboats and two RAF helicopters were scrambled to search for the boy.

He was eventually found by one of the helicopter crews but was dead on arrival after being airlifted to Coleraine Hospital.

All three survivors were said to be suffering severe shock and were detained in hospital.

The surviving child was also thought to be suffering from hypothermia.

It is understood the family come from Belfast and had been visiting the Giant's Causeway as part of their holiday.

Liam Colqhoun, watch manager at Belfast Coastguard, said there was little obvious sign of the danger on a particularly dangerous night.

He said: "The swell had been building up through the evening, although this would not have been immediately apparent.