Authorities in Spain searched Saturday for a member of an Islamic extremist cell that staged vehicle attacks in Barcelona and a seaside resort, focusing on links with his Moroccan comrades, a missing imam believed to have radicalized them and a house that blew up days ago.

Catalan police said the manhunt was centered on Younes Abouyaaquoub, a 22-year-old Moroccan suspected of driving the van that plowed into a Barcelona promenade packed with pedestrians Thursday, killing 13 people and injuring 120. Another attack early Friday killed one person and wounded five in the resort of Cambrils.

But the investigation was also focusing on a Moroccan imam who is thought to have radicalized the cell and was believed to have died on the eve of the Barcelona attack, police said.

Even with Abouyaaquoub still at large, Spanish Interior Minister Juan Ignacio Zoido declared that the terrorist cell responsible for the carnage had been effectively "broken" after five members were killed by police in a shootout, four were in custody, and as many as two were killed in an explosion earlier in the week.

He said there was no new imminent threat of attack.

The manhunt spanned Spain and southern France, with Spanish police searching nine homes in the northeastern town of Ripoll, where most of the suspects lived, and two buses in northwest Catalonia.

Across the Pyrenees, French police carried out extra border checks on people coming from Spain.

Police also conducted a series of controlled explosions Saturday in the town of Alcanar, south of Barcelona, where the attacks were planned in a rental house that was destroyed Wednesday by an apparently accidental blast. Authorities had initially thought it was a household gas accident, but took another look Friday and returned on Saturday.

Initially, only one person was believed killed in the Wednesday blast. But officials said DNA tests were underway to determine if human remains found there Friday were from a second victim.

A police official, speaking on condition of anonymity, said investigators believed a Moroccan imam, Abdelbaki Es Satty, might have been the second victim of the house explosion.

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Muslim residents of Barcelona hold messages reading 'I am a Muslim Catalan, I am not a terrorist. Islam is peace' and 'We are also afraid' as they demonstrate on Las Ramblas boulevard in Barcelona on Saturday. (Lluis Gene/AFP/Getty Images)

Police on Friday searched his home in the northern town of Ripoll. A search warrant seen by The Associated Press authorized police to extract any terrorism-related "weapons, ammunition, explosives, instruments, documents or papers" found.

Es Satty wasn't there, and the president of the mosque where he preached, Ali Yassine, said he hadn't seen him since June, when he announced he was returning to Morocco for three months.

In a notice Saturday posted on that Ripoll mosque, members of the Muslim community denounced the vehicle attacks and offered their sympathy to the families of the victims.

The Islamic State in Iraq and Syria (ISIS) initially claimed responsibility for the Barcelona attack, which took place on the city's famed Las Ramblas. In a new statement Saturday, it also claimed the attack a few hours later in Cambrils, in which five extremists mowed down people along the boardwalk in the seaside resort.

Fake explosives belts on Cambrils attackers

One woman died and five others were injured in Cambrils before police shot and killed all five attackers. They were armed with an axe, knives and fake explosives belts. The ISIS statement provided no information beyond what had been previously reported.

Authorities said the two attacks were related and the work of a large terrorist cell that had been plotting for a long time from the house in Alcanar, 200 kilometres down the coast from Barcelona.

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Messages of peace and love have been posted to the walls around Las Ramblas in Barcelona. (Jared Thomas/CBC)

The name of the lone suspect at large, Abouyaaquoub, figures on a police list of four main suspects sought in the attacks. All the suspects on the list hail from Ripoll, a quiet, upscale town of 10,000 about 100 kilometres north of Barcelona.

Suspect list also distributed in France

The suspect list was issued throughout Spain and into France, according to a Spanish official and a French police official, who spoke on condition of anonymity.

The French official said Spain had flagged a rented Kangoo utility vehicle that was believed to have been rented in Spain by a suspect in Thursday's attacks that might have crossed the border.

Also named on the list is 17-year-old Moussa Oukabir, whose brother, Driss, reported his documents stolen to police in Ripoll. Ripoll's mayor confirmed the documents were found in one of the vehicles used in the attacks.

The brothers were born and raised in Ripoll, where the family's first-floor apartment was searched Friday. No one was home.

4 in custody, including 3 Moroccans

Neighbours said they were shocked by the news of Moussa Oukabir's alleged involvement. One teenager, who identified himself only by his first name, Pau, said they played together when they were younger and he was "a good boy."

In addition to the five people killed in Cambrils, police said they arrested two people Friday, after the two arrests a day earlier. In custody are three Moroccans and one Spaniard, none with terrorism-related records.

"We are not talking about a group of one or two people, but rather a numerous group," regional Interior Ministry chief Joaquim Forn told Onda Cero radio.

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Police identified four Moroccan men they say were involved in the attacks. Three seen in this photo were gunned down by officers in Cambrils, while the search continues for Younes Abouyaaqoub. (Spanish Police/EPA)

The sheer size of the cell recalled the November 2015 attacks in Paris, in which trained ISIS attackers struck the national stadium, a concert hall, and bars and restaurants nearly simultaneously. Since then, the extremist group has steadily lost ground in its self-declared caliphate in Iraq and Syria, most recently with its defeat in Mosul.

"This shows there is no correlation between what is happening over there with Daesh and the operational capacity of the group," said Jean-Charles Brisard, a French security analyst, using another name for the group.

The attacks unnerved a country that hasn't seen an Islamic extremist attack since 2004, when al-Qaeda-inspired bombers killed 191 people in co-ordinated assaults on Madrid's commuter trains. Unlike France, Britain, Sweden and Germany, Spain has largely been spared, thanks in part to a crackdown that has netted about 200 suspected jihadis in recent years.

The dead and wounded in the two attacks came from 34 countries. Canadian Ian Moore Wilson, the father of a Vancouver police officer, died in the Barcelona attack, while his wife Valerie was injured.

With files from CBC News