Spanish police on Monday shot dead a man who could be Younes Abouyaaqoub, the suspected driver of a van that mowed down pedestrians in Barcelona, amid a massive manhunt for the Moroccan national described as dangerous and likely armed.
"They have shot dead a suspect who could be the perpetrator of the attack," a source close to the probe told AFP on condition of anonymity.
Regional police confirmed a man wearing what appeared to be a suicide belt had been killed in Subirats, a village about 60 kilometres (37 miles) away from Barcelona, without identifying the individual.
Bomb disposal units have been dispatched to the site.
Earlier Monday, police had launched an appeal for information about the 22-year-old fugitive, believed to be the last remaining member of a 12-man cell suspected of plotting last week's deadly attacks.
The other suspects have been killed by police or detained after the vehicle rampages in Barcelona and the seaside resort of Cambrils. The Islamic State (IS) claimed responsibility for the assaults, believed to be its first in Spain.
Authorities on Monday raised the death toll to 15, confirming that Pau Perez, a 34-year-old man found stabbed to death in a Ford Focus outside Barcelona on Friday, was killed by Abouyaaqoub.
The police had fired at the car as it forced its way through a checkpoint shortly after the Barcelona carnage, and later found Perez in the vehicle.
Investigators believe the victim was the owner of the car, which was hijacked by Abouyaaqoub to make his getaway.
Describing Abouyaaqoub as around 1.8 metres (five feet, 11 inches) tall, police tweeted four photographs of the man with short black hair, including three pictures in which he was wearing a black and white striped T-shirt.
He is "dangerous and could be armed," police in Catalonia said.
Spanish authorities were also officially notifying European police of the identity of the suspect to enable the launch of a Europe-wide manhunt.
Investigators seeking to unravel the terror cell have homed in on the small border town of Ripoll at the foot of the Pyrenees mountains.
Several suspects including Abouyaaqoub grew up or lived in the town.
Moroccan imam Abdelbaki Es Satty, aged in his 40s, has also come under scrutiny as he is believed to have radicalised youths in Ripoll.
Police raided more homes in Ripoll on Monday, Catalonia's regional interior minister Joaquim Forn said.
Police said the imam had spent time in prison and had once been in contact with a suspect wanted on terrorism charges but was never himself charged with terror-related incidents.
In Belgium, the mayor of the Vilvorde region told AFP that Satty spent time in the Brussels suburb of Machelen -- a district next to the city's airport -- between January and March 2016.
On the other side of Brussels, the Molenbeek suburb has gained notoriety as a hotbed of international jihadists after the Brussels bombings in March 2016 and the Paris attacks in November 2015.
In the Moroccan town of M'rirt, relatives of Abouyaaqoub have accused the imam of radicalising the young man as well as his brother Houssein.
"Over the last two years, Younes and Houssein began to radicalise under the influence of this imam," their grandfather told AFP.
A neighbour close to the Abouyaaqoub family, speaking on condition of anonymity, said the imam "had recruited Moroccans of Ripoll and planned the attacks".
But Ali Assid, president of the Annour Islamic community that runs the Ripoll mosque where Satty was preaching, said the imam "never sent a radical message, all he preached was really Islam. If he is behind all that, there he must be showing us one face in the mosque and showing another face outside."
Assid said Satty had parted ways with the mosque in late June after Ramadan, as he wanted a vacation of three months -- a request that the group did not agree to.
The imam has been missing since Tuesday. On Saturday, police raided his apartment. They have raised the possibility that he died in an explosion on Wednesday evening at a house believed to be the suspects' bomb factory, where police uncovered a massive cache of 120 gas canisters.
The suspected jihadists had been preparing bombs for "one or more attacks in Barcelona", regional police chief Josep Lluis Trapero told reporters, revealing that traces of triacetone triperoxide (TATP) -- a homemade explosive that is an IS hallmark -- had also been found.
The accidental explosion in the house in Alcanar, south of Barcelona, may have forced the suspects to modify their plans.
Instead, they used a vehicle to smash into crowds on Barcelona's Las Ramblas boulevard as it was thronged with tourists, killing 13 people and injuring about 100.
Several hours later, a similar attack in the seaside town of Cambrils left one woman dead. Police shot dead the five attackers, some of whom were wearing fake explosive belts and carrying knives.