The service took place at the famed Sagrada Familia Basilica designed by the artist Gaudi.
The van attack was followed by a auto attack in the seaside town of Cambrils that left one person dead.
A memorial mass has been held in Barcelona for the victims of Thursday's terror attacks that left 14 people dead.
Spanish police are still hunting the driver of the van that killed 13 at Barcelona's Las Ramblas.
Interior Minister Juan Ignacio Zoido said Saturday the terror cell behind the attacks had been "dismantled", but local officials were more cautious.
The so-called "Islamic State" (IS) has claimed responsibility for the Barcelona attack and a second attack in Cambrils where five men wearing fake suicide belts drove an Audi A3 into crowds on the seafront.
Fears were continuing to grow over the fate of seven-year-old Julian Cadman, understood to be a dual British-Australian national, who became separated from his mother during the Barcelona attack.
With Spain's terror threat level at four out of a maximum five, Barcelona had ramped up security at concerts and festivities.
Harvey Degenerates into a Tropical Wave, showers expected for Cayman
An Air Force Reserve Hurricane Hunter aircraft is being sent into them to investigate at some point Sunday. This system is forecast to track west/northwest around 15 to 20 miles per hour .
It was found on the road to Ripoll, where all the main attack suspects lived, and the third was found in Ripoll itself.
Es Satty in June abruptly quit working at a mosque in Ripoll and has not been seen since.
A top Spanish police official said the cell of 12 people "had planned one or more attacks with explosives" in Barcelona and had also used a vehicle and motorcycle in the attack planning.
"Our thesis is that the group had planned one or more attacks with explosives in the city of Barcelona", Trapero told reporters.
The victims of the terrorist attacks in Catalonia are of 34 nationalities, the Catalan emergencies service said Friday.
Police said they believed the suspects were planning a much larger attack.
"We don't have any specific information on this but it can not be ruled out", he said, adding that border checks had been reinforced immediately after the attacks. Moussa Oukabir's older brother, Driss Oukabir, is reported to be one of those detained.
Victims of the attack came from three dozen countries including Algeria, Australia, China, France, Ireland, Peru and Venezuela, reflecting Barcelona's status as Spain's most popular tourist destination. Another person was killed hours later in a similar attack farther south on the coast in Cambrils.
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