A crowd in Barcelona's main square defiantly shouted "not afraid" Friday following a minute's silence attended by Spanish Prime Minister Mariano Rajoy and King Felipe VI, held for the victims of a double vehicle attack.

Standing silent in the Plaza de Catalunya, Rajoy joined the king and Carles Puigdemont, the president of the Catalonia region where Barcelona is located, in mourning the victims of attacks that left 13 dead and more than 100 injured.

At loggerheads as the separatist Catalan government attempts to break away from Spain, Rajoy and Puigdemont put their differences aside as they held the minute of silence in the square near the scene of the Barcelona attack.

Just after, crowds at the square broke out in loud applause, shouting "I'm not afraid."

Spain is reeling from a double attack on Thursday and Friday that saw drivers in Barcelona and another seaside town,, Cambrils, plough into pedestrians.

Police said they killed five "suspected terrorists" during the night and three others were arrested, although the driver of the van in Barcelona remains at large.