At least 13 people were killed and more than a hundred injured when a white van ploughed into a crowd in the Spanish city on Thursday.
The driver of the vehicle is still on the run.
Spanish police also shot five suspected terrorists dead in a later operation in Cambrils town, close to Barcelona.
Seven people, including police, were injured when car drove into them in the early hours of Friday morning, after the Barcelona attack.
Catalonia’s regional leader, Charles Puigdemont, later told local media explosive belts the dead terrorists had been wearing turned out to be fakes.
Turkey’s President Recep Tayyip Erdogan offered his condolences to Spain’s King Felipe on Thursday following the attacks which he said “showed the brutal face of terrorism once again”.
A minute’s silence is to be held at Placa de Catalunya, the scene of the Barcelona attack, at midday local time (GMT1100) on Friday.
Catalan police have warned access will only be permitted on food and those attending should not wear backpacks.
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