Revellers around the globe are bidding a weary farewell on Monday to an unsettling year filled with challenges to many of the world's most basic institutions, including politics, trade, alliances and religion.

The Pacific island nation of Kiribati was the first in the world to welcome the new year, greeting 2019 with muted celebrations after spending 2018 on the front line of the battle against climate change. Kiribati is made up of low-lying atolls along the equator which intersect three time zones, the first of which sees the new year 14 hours before midnight in London.

Australia's largest city Sydney put on its biggest-ever fireworks display in a spectacular welcome to the New Year, kicking off a wave of celebrations for billions around the world.

The party atmosphere is set to sweep across major cities in Asia, Europe, Africa and the Americas as the clock ticks past midnight. A strong police presence has become a key element of the festivities, to protect crowds that could be targeted in terror and vehicle attacks.

As the world parties, many will also look forward to 2019 and wonder whether the turmoil witnessed during the previous year will spill over into the next.

Header photo: New Year's Eve fireworks erupt over Sydney's iconic Harbour Bridge and Opera House during the fireworks show on January 1, 2019. — AFP