Spanish police searched on Sunday for the man behind the wheel in the Barcelona van attack that killed 13 people, amid growing signs members of the militant group had connections elsewhere in Europe.
Police said security operations were under way in Catalonia and on the French border as they searched Moroccan-born Younes Abouyaaqoub, 22, the only one of 12 suspects still at large who they believe may have crossed into France.
Others implicated in the attack have been arrested, shot by police or killed in an explosion at a house in Catalonia a day before Thursday's van attack on Las Ramblas, Barcelona's most famous boulevard.
"We don't have any specific information on this but it cannot be ruled out," Catalan police chief Josep Lluis Trapero told a news conference in Barcelona when asked if Abouyaaqoub could have crossed into France.
Spanish media say authorities believe Abouyaaqoub drove the van through crowds of tourists and locals walking along Las Ramblas, leaving a trail of dead and 120 injured. Trapero said he could not confirm who was behind the wheel.
Hours after the Barcelona attack, police shot dead five men wearing fake explosive belts in the resort of Cambrils, further down the coast, after they rammed holidaymakers with a car and stabbed others, killing one woman.
A seven-year-old British-Australian boy, Julian Cadman, was confirmed on Sunday as one of 13 killed in the Barcelona attack.
Family members said that Abouyaaqoub had began showing more religiously conservative behaviour within the past year, and refused to shake hands with women during a visit to his birthplace in Morocco in March.
They expressed shock and anger after discovering the alleged involvement in the Barcelona attack of Abouyaaqoub, his brother and two cousins, all originally from the small Moroccan town of M'rirt.
Hannou Ghanimi, Abouyaaqoub's mother, told reporters in Catalonia on Saturday she wanted her son to give himself up to police, saying she would rather see him in prison than end up dead.
Evidence emerged on Sunday that alleged members of the Catalan cell travelled to other European countries.