Spanish police have intensified their hunt for a 22-year-old Moroccan man believed to be the driver of the van used in the Barcelona attack that killed at least 13 and injured more than 130 last Thursday. Younes Abouyaaqoub, understood to be the chief suspect in the attack on Las Ramblas, is thought to be a key member of a 12-strong jihadist cell responsible for the attacks in Barcelona and later in nearby Cambrils.

Police say a man previously reported as a suspect – 17-year-old Moussa Oukabir – was killed in the Cambrils attack. Oukabir was among five men shot dead as they launched their assault on tourists and locals in the coastal town west of Barcelona.

Oukabir is thought to have used his older brother’s documents to hire the vehicle that ploughed into pedestrians in Barcelona on Thursday and to have died along with Said Aallaa, 19, and Mohamed Hychami, 24. All three took part in the Cambrils attack, which left one woman dead and six people injured. All five terrorists involved in the second attack were killed by police. The identities of the other two dead jihadists are yet to be confirmed.

Several of those suspected of involvement in the attacks are thought to come from Ripoll, an inland town of 11,000 people about 60 miles (100km) north-west of Barcelona. Police have since searched the apartment of the town’s imam, neighbours said.

Despite the fact that Abouyaaqoub is still at large, Spain decided to maintain its terrorist threat alert at level four, the second-highest level, declaring that no new attacks were imminent. The interior minister, Juan Ignacio Zoido, said the country would nevertheless reinforce security for popular tourist sites and events that draw large crowds.

Meanwhile in Finland, police said a man who stabbed two people to death in the south-western city of Turku last Friday appeared to choose women as targets, and added that they are treating the incident as an act of terrorism. The suspect, arrested after being shot by police, is an 18-year-old Moroccan. Four other Moroccans have been held, police added.

In Barcelona, police reported that four men in their 20s had been arrested in connection with the attack and remain in custody. Three are Moroccan and one is Spanish. None was previously known to the security services for terror-related reasons. Moussa Oukabir’s brother, Driss Oukabir, is reported to be one of those detained.

Of the 14 people who died in the two attacks, 13 have now been identified, although not all have been named. Five were Spanish, three were German and two were Italian; there was also one each from the US, Belgium and Portugal. People from more than 30 countries are now believed to make up the 130 victims who were wounded in the attacks in Las Ramblas and in Cambrils. A total of 54 were still in hospital this weekend, 12 of them in a critical condition.

Police have also revealed that the terrorists behind the rampage were preparing bigger attacks. An explosion last Wednesday at a house in the more southerly town of Alcanar is believed to have destroyed materials the killers planned to use in larger-scale operations. Earlier reports from Spain had suggested that the terror cell was planning an attack using gas canisters.

“We think they were preparing at least one or more attacks in Barcelona,” Catalan regional police official Josep Lluís Trapero told reporters. “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 more rudimentary way than they had initially planned.”

Police are also reported to be looking for a white Renault Kangoo which is believed to have been rented by the suspects and could have been taken over the border into France.

The attacks in Barcelona and Cambrils took place around eight hours apart last Thursday afternoon and early Friday morning. Catalonia president Carles Puigdemont said that in an echo of the London Bridge attack in June, the five terrorists in the Cambrils car were wearing fake suicide belts when they were stopped.

Police also said an axe and knives were found in the vehicle: one knife had been used to stab a pedestrian in the face before the terrorists were gunned down.

Ben Wallace, the UK security minister, said the terror threat to Britain was rising as Islamic State loses battles and territory in Syria and Iraq. He told BBC Radio 4’s Today programme: “I think the threat is still increasing, partly driven by the fact Isis is collapsing in Syria and people are either unable to get out there to fight for Isis and so look to do something at home – or because people have come back and tried to inspire people with their stories and tales of the caliphate. I think those two things mean that the threat is to some extent increasing.”