Cazeneuve said the activists were suspected of planning violent protests at the talks which kick off on Sunday, a day ahead of the opening ceremony, and run until Dec. 11.

The conference, also dubbed COP21, is seeking to agree a deal that signals a break with a rising reliance on fossil fuels, blamed by a U.N. panel of scientists for causing more floods, heat waves and rising sea levels.

"These 24 people have been placed under house arrest because they have been violent during demonstrations in the past and because they have said they would not respect the state of emergency," Cazeneuve said in a speech in Strasbourg.

Following the Nov. 13 attacks on Paris in which 130 people were killed, the French government declared the state of emergency, banning public demonstrations and giving police extended powers of search and surveillance.