Countless revellers switched into party mode on Sunday across Europe to ring in 2018 after Sydney and Hong Kong earlier welcomed the New Year with dazzling firework displays.
As clocks struck midnight across Europe, Paris was awash with people despite the winter cold.
A storm warning and drizzle failed to dampen spirits on the Avenue des Champs-Élysées where thousands gathered for a light show and a fireworks display at the Arc de Triomphe.
A firework explodes over the Arc de Triomphe as part of the New Year celebrations on the Champs Elysees, in Paris, France, Monday, January 1, 2018. Source: AAP
Nearly 2,000 security force members were deployed to protect the crowd - out of some 140,000 mobilised nationwide to guard against the terror threat which the authorities describe as "still high".
One reveller, who gave his name only as Stephane, insisted that a spate of recent attacks on France were "in the past".
"Life goes on and they (jihadists) are on the retreat," he said.
In Germany, revellers enjoyed an open party watching the fireworks from the Brandenburg Gate.
Fireworks light the sky above the Quadriga at the Brandenburg Gate during New Year's celebrations shortly after midnight in Berlin, January 1, 2018. Source: AAP
In London, more than 100,000 ticket-holders were estimated to have watched the city's firework display from the banks of the River Thames a few moments ago.
The city of Dubai replaced its main midnight fireworks with an incredible laser show on the world's tallest tower, the 828-metre Burj Khalifa, accompanied by music.
Asia
Revellers danced to Auld Lang Syne in Hong Kong as the city staged a stunning pyrotechnics display over its famous Victoria Harbour.
Thousands thronged the harbourside to see the show illuminate the famous skyline as revellers danced to Auld Lang Syne as "shooting stars" were also fired during a 10-minute musical fireworks display.
Fireworks light up Victoria Harbour to celebrate the arrival of the new year 2018 in Hong Kong, China, 01 January 2018. Source: AAP
In the Indonesian capital Jakarta, hundreds of couples attended a free mass wedding provided free by the authorities.
"I am very happy," Aminah, who only goes by one name, told AFP. "I'm happy because it's for free and now I have all the legal documents which I have never had before, thank God."
Australia
Revellers in Australia welcomed in 2018 with a spectacular fireworks displays taking place across the nation and the world amid strict security measures.
More than 1.5 million spectators packed the Sydney foreshore to watch tonnes of pyrotechnics light up the night sky.
The technicolour display was set to include a rainbow waterfall of fireworks cascading off the Sydney Harbour Bridge to mark Australia's legalisation of same-sex marriage following a nationwide postal survey in support of change.
"This is a fabulous way to see out 2017 - the year that four out of five Sydneysiders said a resounding 'Yes' to marriage equality," Sydney Lord Mayor Clover Moore said.
Hollywood heart-throb Hugh Jackman added star power with a 20-second gold-and-silver pyrotechnics set, fulfilling a lifelong dream of designing a firework for his hometown.
Fireworks explode over the Sydney Harbour during New Year's Eve celebrations in Sydney, Monday, January 1, 2018. Source: AAP
Toughest security in years
Stricter security measures have been a key focus this year amid fears that crowds could be targets for vehicle and other terror attacks.
In Australia, the stronger police presence included some officers carrying semi-automatic rifles in Sydney and bollards used as barriers against vehicles.
Earlier in December one man was killed and more than a dozen hurt when a man ploughed a car into a crowd of pedestrians in Melbourne.
"You're going to see more police than ever out, it will be our largest contingent ... (given) the current security environment," Victoria state police acting chief commissioner Shane Patton said.
Other cities are also on alert following deadly vehicle assaults over the past two years in Barcelona, Nice and London.
New York's Times Square celebrations are set to go ahead despite the Arctic chill gripping much of the central and north-eastern United States and Canada.
But revellers there will be guarded by the strongest security presence in years, after two recent attacks apparently inspired by the Islamic State group.
Arrests
More than 230 people have been arrested in Victoria as crowds flocked to Melbourne to welcome in 2018 beneath a 14-tonne fireworks extravaganza across the city.
Police arrested 238 people overnight, including 99 arrests for being drunk and 23 reported assaults.
While the total number of arrests was higher than last year, when 183 people were arrested on New Year's Eve 2016, police are pleased with how the evening unfolded.
"Generally, we saw great behaviour by the crowds overnight, which was encouraging," Deputy Commissioner Andrew Crisp said on Monday.
"There were a small number of people who did the wrong thing but they were dealt with by police so they didn't spoil it for others."
