New York :A giant winter "bomb cyclone" walloped the US East Coast on Thursday with heavy snow and freezing cold that made for treacherous travel conditions and bone-chilling misery.

Four people were reported killed in the southeastern states of North and South Carolina, where icy roads sent vehicles skittering.

A cold wave gripping a large section of the United States had already been blamed for a dozen earlier deaths.

Thousands of flights were cancelled and schools closed in many localities as snow piled up and blizzard conditions began taking hold in the northeast.

Temperatures were so low in northern New York that Niagara Falls -- the giant waterfalls straddling the US-Canadian border -- froze.

Snowfall eased by nightfall but temperatures were set to plunge to 8 Fahrenheit (minus 13 Celsius) and remain sub-freezing all weekend. -AFP