Islands in Polynesia and the Central Pacific have ushered in the new year as the UK counts down to the start of 2017.
Cities in the island nations of Samoa, Tonga and Kiribati were the first to welcome the new year as the clock hit 10am on New Year's Eve in London.
The end of 2016 will be marked in the Chatham Islands and parts of New Zealand shortly afterwards, while celebrations are due to begin in Sydney, Australia, at 1pm London time.
When 2017 reaches the UK capital, thousands of police officers will provide a protective ring around the city's set-piece fireworks display, while tactics have been adjusted following this year's terrorist atrocities in Europe.
Armed police will also be a fixture on the capital's Tube trains as they travel between jobs in a move that is hoped to reassure passengers.
Fears of a mass-casualty terror plot targeting one of the country's New Year events have heightened after lorries were used in devastating attacks on crowded areas in Nice and Berlin.
The British Transport Police (BTP) said it would also be extending the working hours of its officers on the night for a second year running.
BTP Superintendent Andy Morgan said: "We developed and improved our security plan for last year's New Year's Eve event following the atrocities in Paris in the previous November and we, of course, have looked at good security, a thorough security boost following a different type of threat in Nice back in July.
"In general, we have a good eyeline on what could happen, we've got very, very good assets both covert and overt deployed out within the footprint and across London, almost joined at the hip with our colleagues from the Metropolitan Police to make sure that we're working together to provide that security blanket across London."
This year's feverish countdown to midnight will also last longer than usual - an extra second - as a so-called "leap second" is introduced to compensate for a slowdown in the Earth's rotation.
When the clock eventually chimes midnight in London, a total of 12,000 fireworks will paint the night sky during the Mayor's showcase display on the banks of the Thames, watched by around 110,000 people.
Some of the stars the world lost in 2016 will be honoured during the 12-minute spectacle, as David Bowie, Prince and the Two Ronnies, which included the late Ronnie Corbett, are to feature in the soundtrack.
In Edinburgh, the world-renowned Hogmanay street party will see 80,000 punters flock to the city centre to enjoy music from The Charlatans, while Paolo Nutini fronts a concert in the gardens.
But the New Year enthusiasm is at risk of being dampened in northern England and Wales, as rain is set to sweep across areas including Manchester, Leeds and possibly Cardiff at midnight, the Met Office said.
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