A manhunt is underway to find the main suspect in the terror attack on Las Ramblas in the heart of Barcelona, Sky News reported.
Younes Abouyaaqoub, 22, is believed to be the driver of the white van involved in the attack on Thursday afternoon, but was not among those shot dead by security forces later that night.
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 terror cell.
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.

Source: Mena