A critical UN conference aimed at agreeing a new global approach to climate change has begun in Paris.

Negotiators from 195 countries will try to reach a deal within two weeks aimed at reducing global carbon emissions.

Leaders from 147 nations will address the meeting, known as COP21, on Monday. Initiatives aimed at boosting clean technologies are due to be launched.

But the world's poorest countries say they fear being "left behind" in the push for a new treaty.

The French government will officially take over the running of the talks during Monday's opening ceremony.

Police have locked down the conference centre in Le Bourget, closing roads amid strict security for the leaders' visit.

Presidents and prime ministers will address the gathering with organisers hoping high-level appearances will boost the chances of reaching a deal to cut emissions.

"It will be the turning point, which is what the world requires," said French Foreign Minister Laurent Fabius at the weekend.

Boost for clean energy

World leaders including President Obama and David Cameron are due to attend the talks. The leaders, who will only stay at the meeting for one day, are likely to make a number of significant announcements.

Under one plan called Mission Innovation, a group of 20 countries - including the US, France and India - will seek to double their investment in clean-energy research over five years.

Private individuals including Bill Gates and Facebook founder Mark Zuckerberg will also invest into low-cost, clean-energy projects, every year from 2020.

In another initiative, France and India will announce a global alliance that aims to bring together 100 solar-rich countries in tropical regions to rapidly expand the availability of electricity from the Sun.

Meanwhile a number of European nations, working with the World Bank, announced a $500m fund designed to help developing countries cut their carbon emissions. Germany, Norway, Sweden, and Switzerland are backing what's termed the Transformative Carbon Asset Facility.

This will measure and pay for emission cuts in areas like renewable energy, transport, energy efficiency, solid waste management, and low carbon cities. According to the World Bank it could make payments for carbon cuts to countries that remove fossil fuel subsidies.