PARIS (AP) — France will reinstate controls on its borders — normally open to other countries in Europe's free-travel zone — for the period around a major U.N. climate conference in Paris, the interior minister said Friday.

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 Nov. 30-Dec. 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.

Activist groups say they were informed that the French controls would begin Nov. 13.

France is still reeling from deadly attacks by Islamic extremists in January on satirical newspaper Charlie Hebdo and a kosher grocery. Since then, the country has seen several other smaller attacks or attempts, including when a heavily armed Islamic radical was prevented by young American passengers from attacking a high-speed train in August.

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.

France faces routine protests that are largely peaceful but sometimes degenerate into violence by an extremist fringe. The country saw particularly violent protests during a NATO summit in Strasbourg in 2009.