France will reinstate controls on its borders — normally open to other countries in Europe's free-travel zone — for the period around a major UN climate conference in Paris, the interior minister said Friday, November 6, the Associated Press reports.

Authorities are on alert for violent protesters as well as potential terror attacks.

Bernard Cazeneuve said on BFM television Friday that the controls will be in place for a month as part of larger security measures around the November 30-December 11 conference. He did not elaborate on how tightly the borders would be controlled or how the border checks would be carried out.

Europe's so-called Schengen zone of countries with open borders does allows for occasional reintroduction of internal border checks, which some countries have done amid this year's migrant crisis.

The climate conference is aimed at reaching the most ambitious accord to date for world governments to reduce emissions that cause global warming.

Organizers expect at least 40,000 people for the conference, in addition to tens of thousands of activists from a broad range of environmental, human rights and other groups from around the world. A major protest march is planned through Paris Nov. 29, in addition to several other smaller-scale actions.