WWF-Hong Kong announced Sunday that Hong Kong will join more than 600 cities in this year's Earth Hour "lights out" campaign, planning to rally more than 3 million Hong Kong citizens' support.

Last year, more than 2 million Hong Kong people participated in Earth Hour by switching off the lights for an hour to respond to the threat of the climate change.

"This simple and meaningful global action clearly showed the world our concerns on climate change. This year, our ambitious target is for 3 million Hong Kong people to join hands with us in Earth Hour 2010 to combat climate change," said Eric Bohm, CEO of WWF-Hong Kong.

"Low carbon Everyday" photo competition aiming to raise awareness and encourage participation for Earth Hour also launched on Sunday.

This year's "lights out" campaign will be carried out at 8:30 p.m. on March 27.