Paris Prosecutor François Molins cast doubt on the identity of a man shot dead by police in the capital on Thursday as authorities sought to establish whether he represented a significant threat or was acting alone and without support.

The man was killed on the first anniversary of deadly Islamist attacks on the Charlie Hebdo satirical magazine in the French capital as he tried to enter a police station wielding a meat cleaver.

An official account said the man, identified by a judicial source soon after the attack as Moroccan-born, shouted "Allahu Akbar," (God is Greatest), and was equipped with what turned out to be a fake suicide belt.

Molins told a French radio station the man may have given a false identity some months ago. He also said a mobile phone found on the body was being examined and contained a German SIM card.

"I am not at all sure the identity he gave was real," Molins told France Inter radio on Friday.

A judicial source said on Thursday that the dead man was Ali Sallah, a Moroccan born in 1995 in Casablanca. He was homeless and known to police for theft in 2012 in the Var region of southern France.

Molins said authorities had established from fingerprints that the dead man identified himself as Sallah to police when they intercepted him last year. However, he said a sheet of paper found on his body gave a different name, and a Tunisian nationality.

Authorities under pressure

The name Ali Sallah was not known to intelligence services.

"We will need to establish the identity — know which is the real identity," Molins said.

Also on the sheet of paper was the Islamic State flag and a claim of allegiance to the militant group written in Arabic.

Islamic State, or ISIS, which controls swathes of Iraq and Syria, claimed responsibility for another deadly attack in Paris on Nov. 13 in which 130 people diedMolins went on to say anti-terrorist authorities were working on 215 cases involving 711 individuals in France. Some 240 people had been taken in for questioning in connection with them. 

He said about half the cases had reached the inquiry stage, and that even though the number of investigating magistrates had risen to 11 from seven last September, anti-terrorism authorities risked being overwhelmed because "since 2012 we have seen a doubling of these cases every year."

Belgian investigators said they believed explosives used in the November Paris attacks may have been made in an apartment in Brussels that was rented under a false name and where a fingerprint of a key fugitive was found.

Police found material that could be used to make explosives, traces of explosive acetone peroxide and handmade belts during a raid on the apartment on Dec. 10.