Sydney - Sydney kicked off New Year celebrations with a spectacular fireworks display as revellers across the globe defied global terror alerts to see in 2017 in style.Around 1.5 million people packed Australia's biggest city to watch as the midnight fireworks erupted from Sydney Harbour Bridge sending rainbow-coloured showers soaring into the night sky. Crowds in Hong Kong also flocked to the waterfront to watch fireworks explode over Victoria Harbour while in Japan thousands packed the streets of Tokyo to release balloons into the air. Bubbles float over visitors during a New Year's Eve celebration in Tokyo. (Koji Sasahara, AP)Shoppers in Japan had earlier filled markets to buy tuna and crabs - seen as expensive items for special feasts - for New Year's Day family gatherings.The celebrations draw to an end a year of bloodshed and misery that has seen the war in Syria, Europe's migrant crisis and numerous terror attacks dominate the headlines.It has also been a year of political shocks, from Britain's vote to leave the European Union to the election of maverick leaders in the United States and Philippines.'Business as usual' Amid global terror jitters, about 2 000 extra officers were deployed in Sydney after a man was arrested for allegedly making online threats against the celebrations.Less than two weeks after the Berlin lorry attack at a Christmas market that killed 12 people, there were a number of reported threats during the holiday period.In Melbourne, police foiled a "significant" Islamic State-inspired Christmas Day terror plot.Indonesia said it thwarted plans by an ISIS-linked group for a Christmas-time suicide bombing, and 52 people were injured in the Philippines in bomb attacks blamed on Islamist militants.Security concerns have hit many New Year events with truck blockades a new tactic to try to prevent vehicles ploughing into crowds, with Sydney using garbage trucks.The German capital has beefed up security after the December 19 attack there, deploying more police, some armed with machine guns."This year, what's new is that we will place concrete blocks and position heavy armoured vehicles at the entrances" to the zone around Brandenburg Gate, a police spokesperson said.Visitors seemed undeterred by recent events as they began to gather under a cold blue sky for a series of concerts ahead of a large midnight fireworks display in the area.In Paris, there will be fireworks again, after muted 2015 celebrations following the massacre of 130 people by jihadists in the French capital.Nearly 100 000 police, gendarmes and soldiers will be deployed across France against the jihadist threat.Brussels, meanwhile, has reinstated its firework show after last year's was cancelled at the last minute due to a terrorist threat.With more than a million people expected to turn out to watch the ball drop in Times Square, New York is deploying 165 "blocker" trucks and some 7 000 police.Thousands of policeRome has stationed armoured vehicles and greater numbers of security forces around the Coliseum and St Peter's Square, where Pope Francis will celebrate a "Te Deum" hymn of thanksgiving.In a Mass earlier on Saturday, the pontiff urged people to reflect on the plight of the young."We have created a culture that idolises youth... yet at the same time paradoxically we have condemned our young people to have no place in society," he said.Moscow police will deploy more than 5 000 officers backed by thousands more from the new national guard and volunteer militia to maintain order.Thousands traditionally gather in Red Square, but for the second year in a row, the area will be open solely to 6 000 invitees.London will have 3 000 officers on patrol with crowds flocking to line the banks of the Thames to watch the fireworks.Up to two million people are expected to party at Rio's Copacabana beach. But with Brazil mired in its worst recession in a century, the fireworks have been cut to just 12 minutes.Normally boisterous Bangkok was seeing in the new year on a more sombre note as the nation grieves for King Bhumibol Adulyadej, who died in October.Thailand's new King Maha Vajiralongkorn urged his subjects to "unite" in a nationally televised speech on Saturday, his first major address to the politically split nation since ascending to the throne.And, at the stroke of midnight, the celebrations will last one second longer - a leap second - decreed by the International Earth Rotation and Reference Systems Service to allow astronomical time to catch up with atomic clocks that have called the hour since 1967.