Fireworks exploded over Sydney's Harbor Bridge as a million onlookers celebrated the New Year.
In London, thousands of revelers gathered to cheer as Big Ben rings in 2007.
In the Australian capital -- one of the world's first major cities to usher in the new year -- people crammed the harbor shore for the lavish fireworks display celebrating the 25th anniversary of the iconic bridge.
But in Thailand, city officials canceled Bangkok's main New Year's Eve celebration Sunday after a series of bombs killed two people and wounded more than 30.
Thousands of revelers who had gathered at the Central World Plaza shopping mall complex for the event were sent home, officials said.
In India, police arrested two suspected Islamic militants about 1 kilometer (half a mile) from the site of New Delhi's main public New Year's Eve celebrations, a report cited police as saying.
Pope Benedict XVI prayed at a New Year's Eve service at the Vatican City in Rome that 2007 would bring the world "peace, comfort, justice."
In London, Big Ben's chimes were to be relayed by sound systems along the River Thames.
More than 200,000 people were expected to crowd the river's banks near the Houses of Parliament to watch a light show countdown projected onto the 443-foot (135-meter) London Eye Ferris wheel.
The event was followed by a 10-minute fireworks display, "big enough and loud enough to be seen ... all over the capital," Mayor Ken Livingstone said.
At least a million revelers were expected to flood Times Square in unseasonably warm New York City to see performances by singers Christina Aguilera and Toni Braxton.
In Romania and Bulgaria, midnight marked a historic milestone, with the two countries becoming the newest members of the European Union.
Fireworks thundered through the sky in the Romanian and Bulgarian capitals, which were decorated with the EU's blue-and-gold flags.
"Welcome to the EU," EU Enlargement Commissioner Olli Rehn told a crowd of tens of thousands at a celebration in Bucharest, where he was joined on stage by Romania's president and European foreign ministers from Germany, Denmark, Austria and Hungary.
Officials were flying later Monday to Sofia for celebrations there.
Bad weather dampened celebrations in other parts of Europe. In Belfast, Northern Ireland, an outdoor concert that was to feature soul singer Beverley Knight and rock band The Thrills was called off due to the threat of gale-force winds.
Glasgow officials said high winds and rain had forced them to cancel traditional Hogmanay New Year's celebrations in the Scottish city. Edinburgh at the last minute also canceled its Hogmanay party, which was to be headlined by the Pet Shop Boys.
In Belgium, several fireworks displays were canceled after two party tents set up for celebrations in northern Belgium blew away on Saturday.
No official celebrations were planned in Paris, but thousands were expected to congregate around the city's most famous avenue, the Champs-Elysees, to welcome 2007.
In the Philippines -- where many believe noisy New Year celebrations drive away evil and misfortune -- police threatened to arrest anyone setting off oversized firecrackers.
Despite the warning, 284 people were injured by firecrackers and celebratory gunfire in the two weeks before New Year's Day, a 75 percent rise from last year, Health Secretary Francisco Duque III said.
"I have campaigned every day against firecrackers," Duque said. "But this has become a deeply rooted part of our culture."
In Japan, thousands climbed mountains, some scaling famed Mount Fuji, to greet the first dawn of the year. Police expected crowds at the summits to reach 15,000.
Many Japanese -- ranging from families with children to elderly couples -- usually start climbing at night so they can reach the top in time for sunrise.
Police anticipated 95 million visitors to the country's major Buddhist temples and Shinto shrines over the first three days of the new year, as people offer prayers for peace, health and prosperity in one of the few religious rites in which most Japanese regularly take part.
The South African city of Cape Town prepared to celebrate New Year's Eve with a show by the Cape Minstrels.
Copyright 2006 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.