A massive security operation is ramping up in France ahead of the UN climate summit this week.

It's a long anticipated event at which world leaders are expected to commit to much tighter targets on carbon emissions.

CNN's Jim Bitterman said protecting the nearly 150 heads of state and 40,000 delegates who are expected at the event will be a real challenge for French security forces.

He said 2800 police and army will patrol the site itself.

8000 more will reinforce French borders and all 120,000 security personnel will be mobilised across the country.