Mourners have gathered for a mass in Barcelona to remember the victims of the terror attacks as a police manhunt continues.

King Felipe VI and Queen Letizia joined politicians at the Sagrada Familia basilica to honour the 14 people killed and more than 120 wounded in Barcelona and nearby Cambrils.

Dignitaries attended the solemn Mass at Barcelona's Sagrada Familia basilica (Manu Fernandez/AP)Dignitaries attended the solemn Mass at Barcelona’s Sagrada Familia basilica (Manu Fernandez/AP)

Spanish authorities have said the terror cell responsible for the attacks has been dismantled, but the search is still on for Younes Abouyaaqoub, a 22-year-old Moroccan who has been named in Spanish media as the suspected driver of the van which was used in the massacre on Las Ramblas that left 13 dead.

The towns of Ripoll and Manlleu are understood to be the focus of the manhunt.

The investigation is also focusing on a missing imam who police believe could have died in a massive house explosion on Wednesday.

Police believe Abdelbaki Es Satty radicalised the young men in the extremist cell, which may have accidentally blown up a house in the seaside town of Alcanar, the Associated Press reported.

Spanish interior minister Juan Ignacio Zoido said five members of the cell were shot dead, four were in custody and as many as two were killed in an explosion.

He said no new attacks were imminent, the country’s terrorist threat alert will be maintained at level four, and security at popular events and tourist sites around the country will be reinforced.

Fears were continuing to grow over the fate of seven-year-old Julian Cadman, understood to be a dual British-Australian national, who became separated from his mother during the Barcelona attack.

Julian Cadman became separated from his mother (Family handout/PA)Julian Cadman became separated from his mother (Family handout/PA)

Speaking after the family made an initial plea for help to find the missing boy, Prime Minister Theresa May said a child with dual British nationality was believed to be among those unaccounted for.

Julian’s father and grandmother are believed to have arrived in Spain on Saturday after travelling from Australia.

Some 34 nationalities were among those wounded in the attacks in Las Ramblas and in Cambrils, which lies around 70 miles to the south west.

Catalan authorities said they have identified some of the victims of the attack in Barcelona as Italian, Portuguese, Spanish, Spanish-Argentine and American. The victim of the second assault in Cambrils has been identified as a Spanish woman.

Spain terror attacks key locations mapped.(PA graphics)

Family members and government officials have said a Belgian and a Canadian are also amongst the dead following the attack in Barcelona.

On Friday it emerged another suspect, Moussa Oukabir, who is thought to have rented the van, was among five men shot dead as they launched a second attack in the coastal town of Cambrils.

The teenager, said to be 17 or 18 years old, is suspected of using his brother’s documents to hire the vehicle that ploughed through pedestrians in the tourist hotspot on Thursday evening.

Politicians and other dignitaries attend the Mass in Barcelona (Manu Fernandez/AP)Politicians and other dignitaries attend the Mass in Barcelona (Manu Fernandez/AP)

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 dead attackers 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. Moussa Oukabir’s older brother, Driss Oukabir, is reported to be one of those detained.

Police said the terrorists behind the rampage were preparing bigger attacks, with the suspected gas explosion on Wednesday in Alcanar believed to have robbed the killers of materials to use in larger-scale operations.