New Year's Eve kicked off in Sydney, but tightened security muted revelries in Europe with Brussels scrapping celebrations and fireworks cancelled in Paris as fears of jihadist threats cast a pall.
Australia's biggest city, Sydney, traditionally the first to host a major event to ring in the New Year, welcomed 2016 with spectacular midnight fireworks as crowds thronged to harbourside vantage points.
Pyrotechnics burst over the city in a colourful display which was expected to draw more than one million people, ahead of the chimes of midnight moving across Asia, the Middle East, Africa, Europe and finally the Americas.
In the heart of Europe, annual festivities and fireworks in Brussels have been cancelled as the Belgian capital -- home to NATO and the European Union -- remains on high alert.
"It's better not to take any risks," mayor Yvan Mayeur said.
Belgian officials are battling terror on two fronts -- with police today detaining six more people over an alleged New Year attack plot in Brussels as well as arresting a tenth suspect over last month's jihadist massacre in Paris.
Officials said two men had already been formally charged with terrorism-related offences and that police detained six more people Thursday for questioning over an alleged plot to strike "emblematic sites" in the Belgian capital during the end-of-year festivities.
Paris, still reeling from the November 13 slaughter of 130 people, has also cancelled its fireworks display.
But authorities agreed France's biggest public gathering since the attacks can go ahead on the Champs Elysees avenue, with bolstered security.
"The people of Paris and France need this symbolic passage into the New Year," said Paris mayor Anne Hidalgo.
"After what our city has lived through, we have to send a signal to the world," she told the weekly Journal du Dimanche.
Hong Kong, Beijing, Singapore and other Asian cities may rival Sydney's pyrotechnic splash, but Brunei will offer a sober evening after banning Christmas in a shift to hardline Islamic law.
Jakarta remains on high alert after anti-terror police foiled detailed plans for an alleged New Year suicide attack in the Indonesian capital.
Turkish police have detained two Islamic State suspects allegedly planning to stage attacks in the centre of the capital Ankara, expected to be packed on New Year's Eve.
In Moscow police will for the first time close off Red Square where thousands of revellers traditionally gather.
"It's no secret that Moscow is one of the choice targets for terrorists," Moscow mayor Sergei Sobyanin said recently.
