The Eiffel Tower, the Sydney Opera House and even the ancient Acropolis in Athens were plunged into darkness for an hour Saturday as part of a global campaign to raise awareness about climate change and its impact on the planet's vanishing plant and animal life.

The 13th edition of Earth Hour, organised by green group WWF, saw millions of people across 180 countries turn off their lights at 8:30 pm to highlight energy use and the need for conservation.

"We are the first generation to know we are destroying the world. And we could be the last that can do anything about it," the charity said.

"We have the solutions, we just need our voices to be heard."

WWF-Australia CEO Dermot O'Gorman told AFP that "Earth hour still is the world's largest grassroots movement for people to take action on climate change".

"It's about individuals taking personal action but joining with hundreds of millions of people around the world to show that not only do we need urgent action on climate change but we need to be protecting our planet," he added.

Dozens of companies around the world said they would take part in this year's campaign, which also saw Singapore's skyline go dark and Hong Kong turn off the lights along the Victoria Harbour.

Other global landmarks that flicked the switch included Eiffel Tower in Paris, New York's Empire State Building, Dubai's Burj Khalifa, the Acropolis in Athens and the Kremlin building in Moscow.

In Hong Kong, major buildings along Victoria Harbour turned off their non-essential lights at 8:30 p.m., and the city's popular tourist attraction known as the Symphony of Lights was canceled.

Over 3,000 corporations in Hong Kong signed up for Earth Hour 2019, according to the WWF Hong Kong website. Iconic skyscrapers including the Bank of China Tower and the HSBC Building in Central, the city's major business district, switched off their lights in response to the global movement.

In Taipei, Taiwan's capital, the island's tallest building, Taipei 101, joined surrounding buildings in shutting off the lights as part of the Earth Hour event.

Beginning in Sydney in 2007, Earth Hour has spread to more than 180 countries, with tens of millions of people joining in.