Cities around the world prepared to welcome the New Year on Monday, from traditional ceremonies in Japan to fireworks displays in Sydney, Dubai, London, Edinburgh and Rio de Janeiro.

At 6 a.m. ET, Auckland, New Zealand, became the first major city to ring in 2019 with fireworks erupting from Auckland's Sky Tower. Thousands of revelers on the waterfront cheered as they watched brightly colored fireworks and laser lighting shoot into the sky over the city's harbor.

Fireworks explode over Sydney Harbor. Brendan Esposito / AP

Celebrations followed in Sydney two hours later with rain-drenched crowds counting down to midnight. Fireworks launched from buildings across the city lit up the night and reflected in the harbor.

Police estimated that more than 1 million people would crowd Sydney Harbor to watch the spectacular display. More than 1 billion people around the world were expected to watch the display on television.

Tokyo also rung in 2019 at 10 a.m. ET, Hong Kong at 11 a.m. ET and Bangkok at noon ET.

While many celebrate New Year's Eve with fireworks and revelry, hundreds of Thais traveled to Takien Temple in a suburb of Bangkok to lie inside coffins for traditional funeral rituals. Participants believe the ceremony symbolizing death and rebirth helps rid them of bad luck and paves the way for rebirth in the new year.

Monks cover worshipers lying in coffins in suburban Bangkok, Thailand, on Monday. Sakchai Lalit / AP

Russian President Vladimir Putin's annual New Year message was transmitted in the Moscow subway system at midnight — 4 p.m. ET — for the first time. The video message will be seen on almost 9,000 screens in 1,820 train cars.

In the Vatican, Pope Francis led the "Te Deum" to thank God for 2018.

Hours ahead of midnight on the East Coast of the U.S., President Donald Trump tweeted an 11-second video saying, "While I'm at the White House working, you're out there partying tonight. But I don't blame you. Enjoy yourselves. We're going to have a great year. Have a really, really happy new year."

Not all was set to be a celebration, however. Across Europe, security has been stepped up.

In Paris, "yellow vest" protesters were calling for more demonstrations on the famed Champs-Elysees, where fireworks, lights and sound show was planned. President Emmanuel Macron was to deliver a televised message.

In London, about 110,000 revelers were expected to gather in official viewing areas for a fireworks display.

But the revelry was being accompanied by a dollop of politics, with the British capital's fireworks celebrating London's “relationship with Europe,” according to the office of Mayor Sadiq Khan.

“The mayor of London’s sold-out event will mark the New Year with a spectacular firework display and soundtrack inspired by the continent,” according to a statement, reflecting Khan’s strongly pro-Europe stance in the run-up to Britain leaving the European Union on March 29.