Spanish police have arrested a Moroccan man suspected of cooperating with a cell behind bloody attacks in Catalonia in August, the interior ministry said Friday.
The 24-year-old man, who was detained in the eastern town of Castellon, was close to several members of the group, especially Abdelbaki Es Satty, who is believed to have radicalised the youths that carried out the attacks, it said in a statement.
He is believed to have helped the cell obtain the ingredients they used to make over 100 kilos of the explosive TATP and provided them with vehicles to transport it.
"Various members of the cell counted on the help of the suspect, who at the very least, provided his personal identification documents which they used to buy hydrogen peroxide, a key ingredient to make TATP," it said.
"In addition, he provided the terrorists with methods of transportation used to move part of the explosives."
In last month's attack, militants killed 16 people using vehicles and knives in a two-pronged attack in Barcelona and the seaside resort of Cambrils, with the bloodshed claimed by ISIS.
Police shot dead six of the suspected members of the cell that carried out the attacks and arrested another four.
Two other suspects -- including Es Satty -- died in an explosion at a house used by the plotters at Alcanar, southwest of Barcelona, on August 16 on the eve of the Barcelona attack.
Police believe the explosion at the house prompted the surviving members of the cell to bring forward their attack plans, resulting in the vehicle rampages in Barcelona and Cambrils.
Spanish police have arrested 201 people they claim are associated with militants since raising the alert level to 4, the second highest, in June 2015.