World protests against fracking

Global Frackdown campaign organiser Mark Schlosberg said there were protests in US cities California, Colorado and New York and large turnouts in South Africa and France.

"It's communities all over the world coming together to say: 'We want to protect our water, we want to protect our air and we want to safeguard our climate future by getting off dirty fossil fuels and saying no to fracking.'

"We need to invest in a renewable energy future," said Mr Schlosberg.

The immense volumes of natural gas found by fracturing underground shale rock have spurred a boom in natural gas production.

But scientists disagree on the risks of hydraulic fracking, a process that injects large volumes of water, sand and chemicals underground to break rock apart and free the gas.

The US Environmental Protection Agency claims that fracking can be done safely.

But opponents say the process can pollute water and sicken residents.

In Pittsburgh protesters signed a petition calling for a moratorium on shale gas drilling.

And in San Francisco Earthworks executive director Jennifer Krill led about 50 demonstrators in a march along the waterfront to the Golden Gate bridge, carrying a 30-foot white banner listing chemicals used in fracking.