Three explosions have been heard at a block of flats in the French city of Toulouse where a man suspected of killing seven people has been holed up since last morning.
The interior ministry could not confirm an assault on the flat had begun.
The blasts were accompanied by flashes of orange light.
Mohammed Merah, 23, is suspected of killing four people at a Jewish school last Monday and three soldiers in two attacks last week.
Earlier, deputy mayor Jean-Pierre Havrin told local media that "negotiations have finished and the assault has begun".
However, sources from the French interior ministry have since been quoted as saying said this was beginning of an operation to apply more pressure on Merah.
Elsewhere in the city, police are hunting for accomplices and have detained several members of Merah's family.