A manhunt is under way to find the main suspect in the terror attack on Las Ramblas in the heart of Barcelona.
According to Spanish newspaper El Pais, police in Catalonia said they were searching for Abouyaaqoub, a Moroccan national living in the Spanish town of Ripoll, who is understood to be a key member of a jihadist cell.
The report comes as new CCTV video shows the speeding van hurtling along Las Ramblas.
In the video a man can be seen desperately pushing a baby buggy out of the way of the vehicle's path.
Of the 12 people police say they are investigating, Abouyaaqoub is the only one who has not been killed or detained.
Police previously believed another suspect, Moussa Oukabir, was the van driver.
It emerged on Friday that Oukabir was among five men shot dead as they launched a second attack in the coastal town of Cambrils.
The 17-year-old is suspected of using his older brother's documents to hire the vehicle that ploughed through pedestrians in Las Ramblas.
He reportedly died along with Said Aallaa, 19, and Mohamed Hychami, 24, who were part of a group that mounted a similar attack in Cambrils that left one woman dead and six people injured.
The identities of the other two shot by police are yet to be confirmed by police.
Four men, aged 21, 27, 28 and 34, who were arrested in connection with the attack remain in custody.
Three are Moroccan and one Spanish, and police said none of them was previously known to the security services for terror-related reasons.
Moussa Oukabir's older brother, Driss Oukabir, is reported to be one of those detained.
Islamic State said those who carried out the attacks had responded to its call to target countries involved in a US-led coalition targeting the group.
The investigation is also centred on a house in Alcanar, southwest of Barcelona, which was destroyed by an explosion on Wednesday night.
Police believe the house was being used to plan one or several large-scale attacks in Barcelona, possibly using a large number of butane gas canisters stored there.
The apparently accidental explosion at the house forced the suspects to scale down their plans and carry out more "rudimentary" attacks.
Catalan regional police official Josep Lluis Trapero told reporters on Friday: "We think they were preparing at least one or more attacks in Barcelona.
"The explosion in Alcanar at least avoided some of the material they were counting on to carry out even bigger attacks than the ones that happened.
"Because of that the attack in Barcelona and the one in Cambrils were carried out in a bit more rudimentary way than the one they had initially planned."
The attacks left 13 people dead in Barcelona and one woman dead in Cambrils.
Some 126 people were injured, with 17 in a critical condition. The dead and injured came from 34 countries.