Gunshots have been heard at the on-going siege at a Toulouse flat where a suspect gunman has been holed up for almost 24 hours, according to news agency Reuters.
At about 10.30pm (GMT) three blasts were also heard at the scene.
An Interior Ministry spokesman has told reporters the explosions "were moves to intimidate the suspect gunman who seems to have changed his mind and does not want to surrender."
The suspect Mohammed Merah is suspected of killing three Jewish schoolchildren, a rabbi and three paratroopers in three attacks in France.
Negotiations between the suspect and police have been continuing on and off since Wednesday morning.
The Toulouse prosecutor, Michel Valet, said: "I cannot confirm that the assault has started. It's not as simple as that. We are waiting."