New Zealand, Australia and Japan are among the countries to have welcomed in 2016.

New Zealand counted down the seconds to midnight with a giant digital clock on Auckland's Sky Tower as it become the first nation with a sizeable population to welcome in the new year.

Horns blared and crowds cheered as the tower was then lit up with fireworks, with colours shifting from green to red to white.

In Australia, simultaneous fireworks displays erupted along Sydney's famed harbour, where people crowded onto balconies, into waterside parks and onto boats as they jockeyed for the best view, clinking glasses and whooping with joy as the first pyrotechnics exploded.

More than 1 million people were expected to watch the glittery display, featuring a multicolored firework "waterfall" cascading off the Harbour Bridge and effects in the shapes of butterflies, octopuses and flowers.

Australian officials, struggling to contain the threat from home-grown extremists, encouraged revellers to enjoy the evening and assured them that thousands of extra police were patrolling major cities.

"Don't change your way of life," Melbourne lord mayor Robert Doyle urged residents of his city. "Don't let events from around the world challenge the way that we live."

New Year's Eve is Japan's biggest holiday, and millions crammed into trains to flee the cities for their hometowns to slurp down bowls of noodles, symbolising longevity, while watching the annual Red and White NHK song competition.

Tokyo is on special alert for security issues this year, with posters in underground stations and other public spaces warning people to keep their eyes open for suspicious packages or activities.