Around 5:00 pm (1500 GMT), a vehicle slammed into a crowd of pedestrians on the famous Las Ramblas boulevard.
Two suspects have been arrested, Catalan President Carles Puigdemont said. According to Spanish newspaper El Periodico, the suspect had been hiding in the Turkish restaurant Luna de Istanbul in the center of the city.
Barcelona's mayor, Ada Colau, said the city would hold a minute of silence on Friday at midday.
Witnesses said the van zigzagged down the busy Barcelona busiest tourist destination -- at the height of the tourist season -- mowing people down and leaving bloodied bodies scattered on the ground.
The tragedy follows other similar terrorist attacks across Europe, many of which involved the use of vehicles. Most recently, a man drove a car into pedestrians, killing four people, on Westminster Bridge in London on March 22.
According to initial reports a van crashed into a crowd in Barcelona's famous Placa Catalunya square at Las Ramblas area injuring several. Source: AAP
People run down a street in Barcelona, Spain, after the attack. Source: AAP
Injured people are treated after a white van jumped the sidewalk in the historic Las Ramblas district. Source: AAP
Mossos d'Esquadra Police officers and emergency service workers move an injured man. Source: AAP
Police officers stand next to the van involved on an attack in Las Ramblas in Barcelona, Spain, Thursday. Source: AAP
Mossos d'Esquadra Police officers set up a security perimeter and identify people near the site where a van crashes into pedestrians in Las Ramblas. Source: AAP
