COPENHAGEN - Tens of thousands of climate activists staged a colourful rally in Copenhagen Saturday to urge negotiators at U.N. talks to agree a strong deal to fight global warming in a worldwide Day of Action.

Bla Bla Bla. Act now!, There is no planet B, Change the politics, not the climate, said banners waved by demonstrators in the Danish capital. Some activists dressed as polar bears, others as pandas -- with a flame rising from their heads.

Some held a giant balloon of an inflatable snowman, under threat of melting from a warming caused mainly by burning fossil fuels that the U.N. panel of climate scientists says will bring desertification, floods, heatwaves and rising seas.

Rallies were held around the world Saturday, hoping to influence delegates half-way through slow-moving 190-nation talks from December 7-18 in the Danish capital to work out a strong, legally binding U.N. deal to fight climate change.

Thousands of Australians held a Walk Against Warming and activists said demonstrations and candlelit vigils were planned from Fiji to the United States to show support for deep cuts in greenhouse gas emissions.

In Copenhagen, estimates of the number of people involved varied from a police estimate of 25,000 to a figure of 100,000 given by organisers, who hope the rallies will put pressure on a summit of 110 world leaders in Copenhagen on December 17-18.

Activists planned a 6 km (4 mile) march out of the city to the Bella Centre where government negotiators from 190 nations are half-way through December 7-18 talks. Activists came from around the world.

SHOUT

This is the right time to shout out and let leaders know this is serious business for us all. Lets hope they listen, said Lin Che, 28, a student from Taiwan.
We want different countries of the world to sign a strong agreement to stop climate change, said Olivier Gilbert, 30, from Lyon in France. If we are 100, it's nothing. If we are 10 million, they will be under pressure.

It's encouraging to see so many people here to let those inside quibbling over words know that it is time to stop talking and act, said Stephanie Fried, 50, from Hawaii.

A police spokesman that the police were also monitoring a separate unauthorised demonstration by activists. Eleven people were detained for disturbing the peace, violating weapons laws or drugs possession, he said.

In Sydney, protesters carried placards saying I like clean energy and I vote, No meat, no heat and No new coal mines, a reference to Australia's status as one of the world's leading exporters of coal.

Inside the conference hall in Copenhagen, delegates claimed progress on some fronts at the halfway mark but the hardest decisions on cuts in greenhouse gas emissions and funding to help the poor are likely to be left for the summit.

We have made considerable progress over the course of the first week, Connie Hedegaard, the Danish cabinet minister who presides over talks, told delegates.

Delegates said negotiators had advanced on texts such as defining how new green technologies such as wind and solar power can be supplied to developing nations and in promoting use of forests to soak up greenhouse gases.

But delegates said there were deep splits on key issues such as raising funds for developing nations and sharing out the burden of greenhouse gas emissions curbs ahead of a closing summit of more than 110 world leaders on December 17-18.

The next week is going to be crucial, said Rajendra Pachauri, head of the U.N. panel of climate scientists.
The Pacific Island of Tuvalu, fearing that rising sea levels could wipe it off the map, stuck to its calls for consideration of a radical new treaty that would force far deeper cuts in greenhouse gases than those under consideration.

The fate of my country rests in your hands, Ian Fry, leading the Tuvalu delegation, told the meeting. I make this as a strong and impassioned plea.

(With reporting by John Acher; editing by Ralph Boulton)