Thousands of Australians stage marches across the nation on Saturday, demanding urgent action on climate change.

In Sydney, thousands walked from Martin Place to the Royal Botanic Gardens, calling for governments to come to an agreement on climate change at Copenhagen.

Max Phillips, one of the organizers, said the march was a way of showing world leaders how deeply concerned Australians were about climate change.

A giant banner bearing the image of a thermometer was unveiled at an event in Newcastle.

In central Melbourne, protesters waving a sea of flags and banners marched down Swanston Street.

Walk Against Warming organizer Tricia Phelan said the next few days were vital in reminding politicians gathered in Copenhagen that Australians want action on climate change.

Hundreds of protesters gathered outside Parliament House in Canberra. The crowd congregated on the Parliament House lawns, blowing whistles, waving placards and chanting slogans calling for a stop to global warming.

In Brisbane, several thousand people carrying placards marched peacefully in steamy conditions through South bank and across the Kurilpa foot bridge, ending with a rock concert in King George Square.