The five assailants, who were wearing what turned out to be fake explosive belts, were shot dead by police.
All of the main suspects are believed to have lived in the north-eastern town of Ripoll.
An imam who police suspect may have radicalised the young men, Abdelbaki Es Satty, is believed to have died in the explosion in Alcanar.
Some few hours later, a similar action was reported at daybreak Friday at a tourist resort of Cambrils, where the members of 12-strong jihadist cell killed another passerby and injured half a dozen using the same modus operandi. The judge will then decide whether they are to be charged.
Abouyaaqoub was shot dead by police on Monday after he was sighted in a village not far from Barcelona.
He stabbed to death a man who was parking his auto and fleeing in the vehicle.
The jihadist behind the wheel of the Barcelona van attack also stabbed a man to death and took his vehicle to escape, Catalonian cops said Monday, as they upped the death toll from last week's carnage to 15.
Investigators seeking to unravel the terror cell had homed in on the small border town of Ripoll at the foot of the Pyrenees mountains.
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. He was also arrested in Ripoll.
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He also spent time in the Brussels suburb of Machelen between January and March 2016.
"Over the last two years, Younes and Houssein began to radicalize under the influence of this imam", their grandfather told AFP.
Thirteen people were killed and more than 130 injured - the casualties came from more than 30 countries - in the first of the attacks last week when a van driver ploughed through pedestrians on the busy Las Ramblas boulevard in Barcelona.
The accidental explosion in the house in Alcanar, south of Barcelona, may have forced the suspects to modify their plans.
Five members of the cell were shot dead, four are in custody and as many as two were killed in the explosion, an interior minister said.
They include Driss Oukabir, whose passport was found in the abandoned van after the Barcelona attack.
Initially thought to be the Barcelona attacker, the 17-year-old Moroccan was killed by police in Cambrils after the auto he was in hit pedestrians before one suspect jumped out and stabbed a woman, killing her.
Hundreds of Muslims rallied Monday at Las Ramblas, holding slogans like "No to terrorism" and "We are Muslims, not terrorists".
On Sunday, the family of a seven-year-old boy killed in the Barcelona attack said they were blessed to have had him in their lives.
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