As police hunted Friday for the driver who plowed into pedestrians on a popular promenade in Barcelona, evidence emerged of a wider plot that could have inflicted even more carnage.
Authorities in the Spanish region of Catalonia had four people in custody and were searching for three others in connection with Thursday's vehicular assault and a similar attack hours later in the resort town of Cambrils, about 80 miles southwest of Barcelona. At least 14 people were killed in all and more than 100 injured.
Investigators were trying to determine whether any of the suspects being sought were among the five assailants fatally shot by police in Cambrils or two people killed in an explosion Wednesday night in Alcanar, a town about 20 miles farther down the coast.
Police believe the plotters, who were all ofMoroccan descent, may have been using the house where the blast took place to build bombs. Had they succeeded, the bloodshed Thursday could have been far more devastating, Catalonia's police chief, Josep Lluis Trapero, told reporters Friday.
The extremist group Islamic State claimed that its "soldiers" carried out the Barcelona attack, which killed 13 people — the deadliest terrorist strike in Spain in more than a decade.
The growing list of suspects and multiple targets recalled the kind of coordination and planning seen in Paris in 2015, when Islamic State-trained attackers armed with bombs and guns struck at a sports stadium, concert hall and other nightspots.
Since then, the group has been losing ground in its self-declared caliphate in Syria and Iraq and has encouraged supporters to plan attacks on their own. More recent assaults in Berlin, London, Stockholm and Nice, France, were carried out by individuals using more rudimentary weapons such as vehicles and knives.
As investigators raced to crack the terrorism network in Spain, two people were killed and six injured by a knife-wielding assailant in Turku, Finland, police said. The suspect was shot in the leg and arrested, according to the Southwestern Finland Police Service.
There were also reports of a person killed and another injured in a stabbing at a store in Wuppertal, Germany. As many as three suspects were being sought in connection with that attack.
The motives for the latest violence were not immediately clear.
Victims of the Barcelona attack included people from at least 34 nations, including the United States and countries across Europe, for whom Spain is a popular vacation destination.
Officials in Europe were beginning to identify those killed, including Jered Tucker, a 43-year-old from Lafayette, Calif., who was in Barcelona on his honeymoon; Elke Vanbockrijck, 44, of Belguim; Bruno Gulotta of Italy; and Francisco Lopez Rodríguez, 60, from the Spanish province of Granada.
An Australian man, Tony Cadman, posted on Facebook that his 7-year-old grandson, Julian, was missing and the child's mother was in serious but stable condition in a hospital.
The bloodshed began Thursday evening when a white van sped down a pedestrian walkway in the middle of Las Ramblas, a popular Barcelona thoroughfare, leaving scores of bloodied people sprawled on the pavement. The driver fled on foot, prompting a manhunt throughout northeastern Spain.
At around 1 a.m. Friday, an Audi sedan carrying five men ran into a group of people near the boardwalk in Cambrils. The men exited the overturned vehicle armed with knives, axes and what looked like explosives belts, which turned out to be fakes, police said.
Six people were injured, including a police officer, before police shot the attackers. One of the victims, a woman, later died of her injuries.
Investigators believe the two attacks were carried out by a large cell and had been in the works for a long time, Trapero said.
Authorities identified three of the five dead assailants: Moussa Oukabir, 17, Mohamed Hychami, 24, and Said Aallaa, 18.
Oukabir is the younger brother of a man whose identity documents were found in the van used in the Barcelona attack. The man, who was arrested Thursday, denies any involvement and has said his brother may have stolen the documents.
Anti-terrorism police were going door to door in the northern Catalan town of Ripoll, where the brothers were born, residents said.
Oukabir was initially suspected to have carried out the attack in Barcelona, but Catalonia's Interior minister, Joaquim Forn, said that no longer appeared to have been the case.
Two years ago, someone using that name said in an online forum that if he were king, he would "kill all infidels and only leave Muslims who follow the religion."
Police were still trying to determine the whereabouts of Younes Abouyaaqoub, 22, and two other suspects.
On Friday, the Las Ramblas walkway quietly reopened to the public, with residents and tourists allowed past police lines to slowly trickle back to their homes and hotels. The city center remained under heavy surveillance.
More than 100,000 people, including King Felipe VI and Spanish Prime Minister Mariano Rajoy, gathered at midday Friday near the promenade for a moment of silence. Afterward, the crowd erupted in applause and chants of "I am not afraid."
The attacks shattered the sense among some tourists that Spain, until now spared the recent spate of Islamist-inspired violence seen in Britain, France and other countries, was somehow safer than the rest of Europe.
On the first leg of their honeymoon, in London, Bianca Passos Fox and her husband, Dan Fox, were on high alert because of the June attack on London Bridge in which three assailants crashed a car into pedestrians before attacking them with knives. The couple let go of some of that anxiety when they landed in Spain for the second part of the trip.
"All I was concerned about was pickpocketing," said Passos Fox, 31, a nutritionist who lives in Brooklyn, N.Y.
The couple spent part of their day Thursday strolling Las Ramblas before ducking into a large indoor market to pick up a bottle of wine for dinner. Less than a minute later, they heard loud banging, and then saw crowds of screaming people rush through the market seeking a back exit. They followed the crowd, even though they didn't know what had happened.
The couple spent much of Friday holed up in their Airbnb. In the afternoon, they ventured out, and passed by the plaza where the van began its violent path. Gone was the former frivolity of tourists enjoying a late-summer holiday.
"I felt this quiet, sullen, eerie energy," Passos Fox said.
A small group of far-right nationalist protesters gathered in the evening to demonstrate near the makeshift memorial erected at the site where the van came to rest after its deadly rampage. "Spain is Christian and not Muslim!" demonstrators chanted while waving flags and banners.
Police clad in riot helmets stood between them and a larger counter-protest, before dispersing the far-right protesters.
Messages of support for Barcelona poured in from across Europe and beyond after the attacks Thursday.. One World Trade Center in New York lighted up in the colors of the Spanish flag, and in Paris the Eiffel Tower went dark.
Special correspondent Cavazos reported from Barcelona and Times staff writers Linthicum and Zavis reported from Mexico City and Los Angeles, respectively. Staff writer Tracy Wilkinson contributed to this report from Washington.
6:20 p.m.: This article was updated with more details about the investigation.
4:10 p.m.: This article was updated with details on the investigation, protests on Las Ramblas and a new witness account.
9:50 a.m.: This article was updated with the stabbing of eight people in Finland, two of whom died, and the shooting and arrest of the alleged assailant.
7:15 a.m.: This article was updated with news of a stabbing in Finland as well as additional details about the victims in Spain.
5:11 a.m.: This article was updated with the arrest of a fourth suspect.
3:40 a.m.: This article was updated with the death of a female victim of the attack in Cambrils.