Abdul Hakim A, a Chechen-born French national who had been held by police for four days before he appeared in court, had been on watch lists prior to Saturday’s stabbing attack which was carried out by his friend Khamzat Azimov.
Azimov killed a 29-year-old man and injured five others, in the busy Opera district of the French capital on Saturday night before being shot dead by police.
Azimov, a 20-year-old naturalised Frenchman of Chechen origin, had been on France’s two main watch lists for suspected radicals since 2016.
Hakim A, also 20, was detained Sunday in the eastern city of Strasbourg, where the two men grew up, and later transferred to the headquarters of France’s domestic intelligence services in Paris.
"He has denied any implication in either preparing or carrying out the acts as well as any recent links with Khamzat Azimov, claiming not to have seen or been in contact with him for several months," according to France’s top anti-terror prosecutor Francois Molins.
But he added that examinations of telephone networks showed that shortly before the attack, Hakim A has sent his sister a text message of "a jihadist chant regularly used by the Islamic State".
Two women were also detained for questioning Thursday in connection with the attack, according to Molins, who declined to give further details.
A source close to the inquiry said one of the women was Ines Hamza, a radicalised 19-year-old who married Hakim A before trying to leave for Syria in January 2017.
Witnesses said Azimov yelled "Allahu akbar" (God is greatest) during the rampage, for which the Islamic State group has claimed responsibility, later releasing a video purporting to show Azimov pledging allegiance to the jihadists.
Investigators want to determine if Hakim A "may have influenced Azimov in his jihadist quest or knew he was planning this attack," the source said.