THOUSANDS returned to Las Ramblas in Barcelona to defy the terrorists and pay their respects to the dead and injured as police were in a race against time to track down four suspects still at large.

Just hours after the twin terror attacks killed 14 people and injured dozens more, the city was trying to return to some semblance of normality.

The centre of the popular tree-lined walkway in the heart of the city was turned into a shrine with people living bouquets of flowers, candles and other tributes.

Yesterday evening, the peace was temporarily marred by a small protest by far-right activists, who were confronted by anti-fascists. Police had to separate the two groups.

Earlier in the day, crowds gathered for a minute's silence in the Placa de Catalunya before parading down Las Ramblas.

The marchers burst into spontaneous rounds of applause, chanting "I'm not afraid!" as they made their way down the bustling tourist hotspot, packed with bars, restaurants and market stalls.

Aamer Anwar, the Scottish lawyer and rector of Glasgow University, who was witness to Thursday’s attack, said: "Life seems to be going back very quickly to normality.”

He praised the "sea of humanity," that had helped those in need during the attacks and said there was a sense locals were determined not to let the atrocities divide them.

"There is almost a spirit here that Barcelona will carry on. It seems to be the approach that people are adopting; that they won't be divided, they won't allow these people to succeed,” he declared.

Last night, Catalan police released the pictures of four suspects, believed to be members of the terrorist cell, which committed the atrocity in Barcelona on Thursday evening and then at Cambrils, 70 miles south, early on Friday morning. Vans were used in both incidents to kill and injure people.

The wanted men were named as Moussa Oukabir, Mohamed Hychami, Younes Abouyaaqoub and Said Aallaa.

Oukabir, 17, a Spanish national of Moroccan descent, is thought to have stolen the identity of his older brother Driss, 28, to rent the vehicle used in the Barcelona attack. He is said to have also rented another van found hours later in the town of Vic, north of the city, which was intended as a getaway vehicle.

The Catalan police suggested the terror cell with as many as 13 members had been preparing bigger atrocities than those they eventually carried out.

As a fourth arrest was made in connection with the deadly vehicle attacks, the authorities revealed that a suspected gas explosion on Wednesday further down the coast at Alcanar robbed the killers of materials to use in larger-scale operations. It is thought they intended to use gas canisters to cause explosions.

Josep Lluis Trapero, the police officer leading the investigation, told reporters that the blast at a house in Alcanar meant the attacks were more "rudimentary" than planned.

"We are working on the hypothesis that these attacks were being prepared for a while around this private home in Alcanar. 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," explained Mr Trapero.

He added that one of the five terrorists killed by police during the terror attack in Cambrils might have been the driver of the van which killed 13 people in Barcelona. Local reports that this was indeed the case were, however, not confirmed by the authorities last night.

Four men are in custody, aged 21, 27, 28 and 34. Three are Moroccan and one Spanish, and police said none of them was previously known to the security services for terror-related reasons.

Speaking at Chequers, Theresa May said Britain stood “shoulder to shoulder with Spain in confronting and dealing with the evil of terrorism and I have offered any assistance we can provide”.

She added: "Sadly, I must tell you that we do believe that a number of British nationals were caught up in the attack and we are urgently looking into reports of a child believed missing, who is a British dual national."

This is believed to be seven-year-old Julian Alessandro Cadman, said to have been born in Kent but who moved to Australia three years ago. He is thought to have been separated from his mother as the attack in Barcelona unfolded.

His grandfather Tony Cadman, originally from Dorset but who lives in Sydney, posted a photograph of Julian, writing: "My grandson, Julian Alessandro Cadman is missing. Please like and share.”

Among those confirmed dead are: Bruno Gulotta, 35, from Legnano near Milan in Italy, who was on holiday in Barcelona with his partner and two children; Elke Vanbockrijck, 44, from the Belgian town of Tongeren, is understood to have also been on holiday in Barcelona with her husband and two sons; Luca Russo, 25, an engineering graduate from Bassano del Grappa in northern Italy, thought to have been in the city with his girlfriend when the attack unfolded and Spaniard Francisco López Rodríguez, 57.

Rex Tillerson, the US Secretary of State, confirmed that one of the 14 dead was an American.

Some 34 nationalities were among almost 130 people wounded in the attacks.

Three days of mourning have been declared by the Government of Catalonia.