Explosions have been heard outside an apartment in Toulouse as French police try to pressure a gunman accused of killing seven people into ending a stand-off now in its second day.
Self-declared al Qaeda militant Mohammed Merah has been holed up in the ground floor property since the early hours of Wednesday.
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Negotiations have continued all day but Merah reportedly said he would surrender at night "to be more discreet".
The series of blasts began at around midnight local time (11pm GMT) and have continued periodically throughout the night. It is being reported that police have been exploding charges to intimidate the suspect.
The deputy mayor of Toulouse had said an assault on the building had begun - a claim then denied by interior ministry official Pierre-Henry Brandet.
Mr Brandet said: "There were moves to intimidate the gunman who seems to have changed his mind and does not want to surrender. There is no assault."
Explosions rocked the district of the southwestern city and orange flashes lit up the sky.
Reuters news agency cites a police source as saying the blasts blew open the door of Merah's apartment but local French media reported that the wanted man was still inside.
There were also reports of gunfire at the site. Merah is thought to be armed with a Kalashnikov assault rifle, a Mini-Uzi submachine pistol and a collection of handguns.
Street lighting in the area was turned off earlier as officers continued to surround the apartment block.
The 23-year-old, a French national of Algerian descent, is suspected of killing three Jewish schoolchildren, a rabbi and three paratroopers in a wave of attacks in southern France in recent days.
He has reportedly told police that he carried out the murders to "avenge Palestinian children".
He had also admitted that he planned to kill a soldier on Wednesday morning.
"This will not last for days, because of physical and mental fatigue. All the experience with crazed gunmen like this is that they stop at some point," defence minister Gerard Longuet said on TF1 television.
"What we want is to capture him alive, so that we can bring him to justice, know his motivations and hopefully find out who were his accomplices, if there were any," he added.
President Nicolas Sarkozy has said Merah wanted to bring the nation "to its knees".
The politician, speaking at a memorial service for three soldiers killed by the gunman last week, said the killer had failed to divide France.
The scooter allegedly used in the attacks has been seized by police.
The French prosecutor handling the case, Francois Molins, said Merah had been to Afghanistan twice and had trained in the militant stronghold of Waziristan.
His brother, who has been arrested, had been implicated in a network sending fighters to Iraq.
A car belonging to him has also been seized after it was said to contain explosives.
Mr Molins told reporters the US army sent Mohammed Merah back to France after he was arrested in Afghanistan.
Afghan police apparently detained the man at a road checkpoint and handed him over to the US army "who put him on the first plane headed to France," he said.
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