Australia celebrated its first restriction-free New Year's Eve after two years of COVID disruptions, as the world began bidding farewell to a year marked for many by the war in Ukraine, economic stresses and the effects of global warming.

Sydney, one of the world's first major cities to welcome in the New Year, did so with a typically dazzling fireworks display, which for the first time featured a rainbow waterfall off the famous Harbour Bridge.

"This New Year's Eve we are saying Sydney is back as we kick off festivities around the world and bring in the New Year with a bang," said Clover Moore, lord mayor of the city, ahead of the events.

Lockdowns at the end of 2020 and a surge in Omicron cases at the end of 2021 led to crowd restrictions and reduced festivities in Australia. However, curbs on celebrations were lifted this year after Australia, like many countries around the world, re-opened its borders and removed social distancing restrictions.

The display in Sydney featured thousands of fireworks launched from the four sails of the Sydney Opera House and from the Harbour Bridge.

In China, rigorous COVID restrictions were lifted only this month in the government's reversal of its "zero-COVID" policy, a switch that has led to soaring infections and meant some people were in no mood to celebrate.

"This virus should just go and die, cannot believe this year I cannot even find a healthy friend that can go out with me and celebrate the passage into the New Year", wrote one social media user based in eastern Shandong province.