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. The city's deputy mayor confirmed an assault on the flat, surrounded by police for nearly 24 hours, 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. "Negotiations have finished and the assault has begun", deputy mayor Jean-Pierre Havrin told local media. Police had been negotiating with Merah, said to be heavily armed, but had not convinced him to surrender. Police surrounded Merah's block after two officers were shot at when they tried to get into his flat early on Wednesday morning. Officials say he is heavily armed with a Kalashnikov high-velocity rifle, a mini-Uzi 9mm machine pistol, several handguns and possibly grenades.