Throngs of revelers packed cities around the globe to usher in 2018 with public celebrations and fireworks, despite fears of terrorism and frigid weather in some places.
In New York, hundreds of thousands of people packed Times Square in the 9-degree Fahrenheit weather, with a wind chill of 4 degrees below zero, to watch the 2018 ball drop and confetti rain down on the street. The frigid temperature made it the second coldest New Year's Eve ball drop on record in New York. The coldest ball drop still holds at 1-degree Fahrenheit in 1917.
Law enforcement agencies had added additional security measures, including extra checkpoints, police dogs, street closures and undercover officers.
"You will see a stronger police presence out there than we've seen, even than what we've seen in recent years. And that's prudent, given the terror events we have seen and studied around the world as well as the three incidents here in New York over the past 15 months," said NYPD Commissioner James O'Neill before the East Coast clock struck midnight.
And in Las Vegas, where a gunman killed 58 people at a music festival in October, officials installed extra security -- including National Guard officers and snipers on rooftops -- along the famed Las Vegas Strip. Fireworks lit the sky in a synchronized spectacle over the city as the new year began.
In San Francisco, fireworks burst over the waterfront amid a heavier-than-usual police presence. Security was intensified after a man had been arrested in December for allegedly seeking to attack a popular San Francisco tourist site on Christmas Day.
Around the world, cities celebrated the New Year with spectacles of fireworks.
More than a million people lined the harbor in Sydney, Australia, to watch a 12-minute fireworks show over the iconic Opera House and Harbour Bridge. Across Asia, people crowded into waterside viewing areas to see fireworks burst over Shanghai, Singapore, Hong Kong and other cities.
In Moscow, revelers filled special New Year's subway trains decorated with winter scenes. And Pope Francis led his annual Te Deum prayer at St. Peter's Basilica in Rome.
After a year marred by mass shootings and deadly terror attacks, many celebrations unfolded amid heightened security.
In London, officials deployed armed officers as part of a security plan they "developed and reviewed following the tragic incidents that have occurred throughout the year," Metropolitan Police Superintendent Nick Aldworth said.
After a spate of sexual assaults marred New Year's Eve events in several German cities in 2015, officials in Berlin this year set up a special "safe zone" for women who feel harassed. Berlin, Cologne and other German cities also added hundreds of extra police.
In Paris, 1,850 police officers were assigned to the Champs-Elys-es amid a "double perimeter of security," Interior Minister G-rard Collomb told BFMTV.
And almost a year after a gunman opened fire on 2017 New Year's revelers in an Istanbul nightclub, Turkish police raided a suspected ISIS cell last week to help thwart potential attacks during the holidays.
Across North America, New Year's celebrators grappled with record low temperatures, as the holiday was expected to be 20 to 40 degrees colder than usual in many places.
Of the lower 48 US states, only 10 aren't under a wind-chill alert.
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