A 21-year-old man arrested on suspicion of stabbing a French soldier in the neck in Paris was flagged to French intelligence months ago over fears that he had been radicalised, it was claimed.
Alexandre D, as the French suspect has been called, was arrested at a friend's flat in Yvelines, just west of Paris.
Investigators are seeking to determine whether the Paris attack last weekend was inspired by the Islamist murder of a British serviceman in London.
Contrary to earlier claims by the Interior Ministry and Paris prosecutor, police sources told Le Monde French intelligence was recently warned that the suspect, who converted to Islam about three years ago, was "becoming increasingly radical".
The warning came in a note written by the police intelligence unit of the Yvelines area where Alexandre D was arrested.
The note provides a fairly detailed account of the suspect's evolution towards a more radical form of Islam since 2009, pointing out that police had remarked he had "suspicious behaviour".
Homeless and unemployed, Alexandre D applied for jobs in Rambouillet where he "demanded not to work with women".
He also came under scrutiny after a street prayer in 2007 while authorities had his DNA profile on record after a series of petty crimes as a minor.
Detectives identified him through video footage, in which he can be seen praying near the crime scene eight minutes before the attack, as well as buying two knives an hour before. DNA was also found on items left at the scene in a plastic bag, including a knife and a fruit juice bottle.
Francois Molins, the Paris prosecutor, said the suspect "owned up to the attack" shortly after his arrest and added that he "acted in the name of his religious ideology".
The prosecutor denounced the suspect's "quite clear intention to kill" Cedric Cordiez, 23, who was attacked from behind.