About 20 Chinese cities joined a worldwide relay on Saturday night to switch off lights of major buildings for one hour to highlight concerns about climate change while calling for actions.

Tens of thousands of Chinese either turned off lights and appliances at home or joined outdoor activities such as candle-lit dinners and star-gazing parties, to show their support.

The iconic "Bird's Nest" National Stadium and the "Water Cube" National Aquatics Center in northern Beijing, usually illuminated by floodlights, went dark completely at 8:30 p.m. local time (1230 GMT).

Dozens of glitzy hotels, office buildings, shopping malls and restaurants in the capital also switched some lights off for 60 minutes.

At a hotel next to the "Bird's Nest", more than 100 officials, dignitaries and journalists gathered to witness the symbolic ceremony which unveiled the China leg of Earth Hour, the global campaign organized by the World Wide Fund for Nature (WWF).

"I hope tonight's activity will inspire everyone to make energy saving a daily habit," Chinese actress Li Bingbing, an ambassador of Earth Hour campaign in China, said at the ceremony.

Famed Chinese pianist Lang Lang also appeared in a short video clip on the popular website Youtube.com, appealing his countrymen to "turn off lights" and support climate change action.