France reintroduced border checks on Friday as it tightened security ahead of UN climate talks that start in Paris at the end of the month.

Controls will be in place until December 13 at 285 road, rail, sea and air border points.

About 30,000 police will be involved in the operation.

US President Barack Obama, his Chinese counterpart Xi Jinping and Indian Prime Minister Narendra Modi are among more than 115 heads of state and government attending the 21st United Nations Climate Change Conference to be held at Le Bourget outside Paris from November 30 to December 11.

The conference aims to agree a new global pact to fight climate warming.

French Interior Minister Bernard Cazeneuve has said the risk of "terrorist threat (or) public disturbance" during the conference cannot be dismissed.

French security sources are paying particular attention to militant ecologist protesters already active around the site of a new airport under construction at Notre-Dame-des-Landes in western France and potential attempts to disrupt the train line linking the southeast French city of Lyon with Turin in northern Italy, sources said.

The potential involvement of extreme-left militant groups in demonstrations timed to coincide with the climate conference is also being watched closely.

The tightening of France's borders comes as Europe's cherished Schengen zone is buckling under the pressure of the biggest migrant crisis since World War II.

France has said it is able to temporarily abandon its commitments to border-free travel guaranteed under the Schengen agreement in special circumstances such as the climate talks.

Obama to still participate in Paris climate talks: US official
Washington (AFP) Nov 14, 2015 - US President Barack Obama still plans to participate in a UN climate conference near Paris in two weeks, despite attacks that killed 128 people in the French capital, a US official told AFP Saturday.

Obama is scheduled to attend the talks which begin on November 30 at Le Bourget, on the northern rim of Paris, and aim to secure a deal staving off catastrophic levels of global warming caused by greenhouse gas emissions.

At this point, no change is planned in Obama's attendance, the official said.

Islamic State jihadists have claimed the series of coordinated attacks Friday by gunmen and suicide bombers who killed at least 128 people in scenes of carnage at a concert hall, restaurants and the national stadium.

French Foreign Minister Laurent Fabius said Saturday the climate conference would go ahead as planned.

"COP21 must be held," he said, using the conference's technical name, but he added that security would be increased.

Obama has championed reducing climate change, saying he hopes an ambitious and sustainable deal will come out of COP21.

Earlier this month Obama blocked the Keystone XL oil pipeline that Canada sought to build into the United States, ruling it would hinder the fight against climate change.

The November 30-December 11 climate talks take place under the UN Framework Convention on Climate Change.