The lights go out on Sydney Harbour Bridge, as Earth Hour 2012 works its way around the globe.

The Opera House was also blacked out for the event - which sees iconic buildings around the world cast into darkness for one hour in an attempt to raise awareness about energy consumption.

(SOUNDBITE)(English) MONICA BERGIN, LOCAL RESIDENT, SAYING:

"I think it's brilliant. It's a good example for the rest of the world and it originated here in Sydney, and the less energy that's used around the globe the batter."

More than 130 countries will take part in the blackout.

Here in the South Korean capital, the Seoul Tower switched its lights off, but one resident says the symbolic action is not enough.

(SOUNDBITE) (Korean) 46 YEAR-OLD YOON WON-GOO, SAYING:

"The lighting-off event is good, but I think the world also needs to cut back on driving cars and building thermal power plants."

Earth Hour has grown from a one-city initiative in 2007 into a global movement which this year will see the lights go out on many of the world's most famous landmarks, including the Great Wall of China, the Eiffel Tower, and the Empire State Building.

Nick Rowlands, Reuters.