The world rang in the New Year on Saturday with a string of spectacular firework displays watched by millions to mark the beginning of 2012.

Sydney and Hong Kong set the standard with glittering extravaganzas staged over the harbours but the mood was more sombre in Tokyo where celebrations were overshadowed by memories of January's earthquake and tsunami.

London meanwhile geared up for a display over the River Thames to usher in a year in which it will host the Olympic Games for the first time in over 60 years.

Tens of thousands of revellers were expected to descend on Scotland's capital Edinburgh to attend its Hogmanay street party. The city will see around 80,000 party-goers welcome in 2012 before erupting into a mass rendition of "Auld Lang Syne".

Sydney kicked off the celebrations. On the stroke of midnight the harbour exploded in a blaze of colour and light that drew more than 1.5 million people to crowded foreshores and city landmarks.

Shapes of clouds and hearts floated above Australia's biggest city, while glittering lights cascaded off the focal point of the display, the Sydney Harbour Bridge, and fireworks launched from barges and rooftops exploded overhead.

"Every year we make sure our celebrations are bigger and better than the one before," Sydney Lord Mayor Clover Moore said.

Two hours later there were celebrations in Tokyo as the clock struck midnight with balloons released, fireworks set off and the Tokyo Tower lighting up in blue.

It was then Hong Kong's turn in the limelight with the city's harbour lit up by a barrage of fireworks fired from several of its iconic buildings, delighting partygoers crammed on to the waterfront and in pleasure boats on the water.

Russia's Far Eastern regions of Chukotka, Kamchatka and Magadan, eight hours ahead of Moscow, became the first parts of the vast country to see in the New Year at 1200 GMT.

Russian state news agencies reported that among the first revellers in 2012 were border guards on Ratmanov island in the Bering Strait that lies just four kilometres from US territory across the international dateline.

In Moscow thousands gathered in Red Square for another massive firework display sending rockets 140 metres (400 feet) into the midnight sky.

But the sale of all alcohol was banned in a bid to prevent the revelry getting out of hand.

And the mood was less festive in Russia's second city of Saint Petersburg, where last-minute gift shoppers worried about the economic hard times ahead.

"I expect that things will be worse next year, especially from the economic point of view. I fear that the next year is going to be very hard," said Galina Fedorchenko, 59.

As the clock moved through the timezones partying began at Berlin's Brandenburg Gate, in the heart of Vienna and on Paris's Champs-Elysees avenue.

Last year's "Silvesterpfad" event in the Austrian capital attracted 750,000 people to hear the New Year rung in by the great bell of Saint Stephen's Cathedral, followed by the strains of the Blue Danube Waltz.

In Amsterdam, revellers were preparing for the first "kiss" between two giant inflatable puppets representing a Dutch boy and girl, which will "walk" towards each other as the seconds tick down to 2012.

At the stroke of midnight, the puppets will kiss as fireworks explode in an event organisers hope will become a yearly tradition in the city.

In the Paris area the purchase of petrol in cans was banned in a bid to prevent a wave of car burnings that occurs annually in some quarters, while 10,000 police were mobilised.

In Rio, two million white-clad party-goers -- Brazilians and foreign tourists -- are expected to ring in the New Year on Copacabana beach, watching a spectacular "green" fireworks extravaganza.

And more than a million revellers are expected to flock to New York's Times Square where pop diva Lady Gaga and tenor Placido Domingo are among the star-studded lineup, and the traditional crystal ball drops at the stroke of midnight.

Mounted officers, bomb-sniffing dogs and police patrol boats were part of a massive police deployment to ensure the party passes off without a hitch.

New Zealand was among the first places to see in the New Year but heavy rain over most of the country put a damper on parties, with two major celebrations in the North Island cancelled due to the weather.

In Japan, still suffering the effects of the March 11 earthquake and tsunami that triggered a massive radiation leak from a nuclear power plant, families gathered for trips to shrines to mark the New Year.

But nuclear evacuees said they had little to celebrate after being relocated far from home and loved ones.

"I can't say Happy New Year as I don't feel happiness," said Yuji Takahashi, one of about 1,000 refugees living in a 36-storey Tokyo tower block.

In the Philippines, where killer floods spawned by tropical storm Washi have swept away whole villages in the country's south, the normally festive New Year's Day was also expected to be a sad and sombre occasion.