Sydney extravaganza to kick off New Year celebrations around the globe

Australia's largest city Sydney will welcome 2018 with a rainbow-themed fireworks spectacular marking new same-sex marriage rights on Sunday, with heavy security for festivities that kick off a wave of celebrations around the world.

The first major New Year's bash will see more than 1.5 million spectators pack the city's foreshore as tonnes of pyrotechnics light up the night sky.

The technicolour display will 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 vote 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 heartthrob Hugh Jackman will add star power with a 20-second gold-and-silver pyrotechnics set, fulfilling a life-long dream to design a firework for his hometown.

The chimes of midnight then move across the world to Asia, the Middle East, Africa, Europe and finally the Americas.

Dazzling light shows will bid farewell to 2017.

Hong Kong: "Shooting stars" to be fired off from the rooftops of buildings in a 10-minute musical firework display

Singapore: More landmarks are included in the countdown party, with a symphony of light and sound illuminating the waterfront skyline

Tokyo: People traditionally spend the eve with their families at home, while many young people head downtown for countdown events

Dubai: The city is replacing its main midnight fireworks with a laser show on the world's tallest tower, accompanied by music

Moscow: Major boulevards and squares will be decked out to welcome the new year, with fireworks to light up 36 key sites

Rio: Millions will gather on Copacabana beach to watch fireworks, with many wearing white, the traditional dress to usher in the new year

Stricter security measures will be a key focus amid fears that the huge crowds in public places could be targets for vehicle and other terror attacks.

People in Sydney waiting for new year fireworks to begin later in the day | Photo: Reuters

In Australia, the beefed-up police presence will include some officers carrying semi-automatic rifles in Sydney and bollards used as barriers against vehicles.

The heightened measures come just a week after more than a dozen people were 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 preparing for possible threats following deadly vehicle assaults over the past two years in Barcelona, Nice and London.

New York's Times Square celebrations will be safeguarded by the toughest security presence in years, after two recent attacks apparently inspired by the Islamic State (IS) extremist group.

IS's defeat in Iraq was one of the key stories this year, although the jihadists remain a threat and numerous attacks around the world were claimed by them or Al-Qaeda -linked groups.

Donald Trump has stolen the spotlight as he made his debut as US President in 2017, with "America first" policies and a bombastic personal style that has shaken international diplomacy.

The former reality television star is likely to continue to dominate headlines in 2018, with escalating tensions over North Korea among a host of global challenges going into the new year.