Police say a “massive crash” in Barcelona city centre in which several people are feared to have been killed is a terrorist attack.
A white van mounted the pavement of Las Ramblas, the main tourist area in the city, and struck several people, police said.
It came to a halt at the entrance to the Liceu metro station and the occupants escaped and ran off into the streets nearby, according to one newspaper.
Spanish radio station Cadena Ser Radio and El Pais newspaper say 13 people have died and various newspapers say at least 20 have been wounded.
Catalan police have confirmed there is at least one dead and 32 injured, 10 seriously.
Catalonia’s regional interior chief Joaquim Forn said during a news conference on Thursday: “Unfortunately the number of fatalities will likely rise.”
Two armed men have since entered a Turkish restaurant and have taken hostages, one TV station is reporting.
El Pais says the perpetrators are holed up in a bar in the Raval district, on Calle Tallers, towards the end of Las Ramblas but other reports say they are in another bar further south, on Carrer de l’Hospital.
Police have said they are looking for a man of 5ft 5ins (1.7m) in height, wearing a white shirt with blue stripes.
The van used in atrocity is said to be a Fiat, that was hired from an address in Santa Perpetua Of the Mogoda about five miles outside the city.
El Pais has identified a man who the Civil Guard says is responsible. A Facebook account says he is from Marseilles and lives in Ripoll, Catalonia, about 50 miles north of Barcelona.
TV3 says that security forces have found a second van in which the attackers may have fled in the town of Vic, 40 miles from Barcelona, 10 miles south of Ripoll, according to police sources.
Footage from reporters on the ground shows armed officers combing a market, with a search said to be under way in several other shopping areas.
One social media video post shows bodies strewn across the pavement for several hundred metres along the famous street.
Numerous people have been trapped in shops after being told to hide following the initial crash. They are slowly being evacuated by armed officers.
Emergency services in Catalonia say they have asked the Metro to be shut down and the Renfe station nearby have been closed and evacuated.
Police have also cordoned off the wide street and shut down several of the shops.
Social media footage showed many people fleeing the area in alarm and a helicopter flying overhead.
The National Police have told people to avoid the Plaza Catalunya area.
An eyewitness, lawyer Aamer Anwar, who’s at a conference in the city, said: “All of a sudden I heard a crashing noise, and the whole street just started to run screaming.
“I saw a woman next to me screaming for her kids.”
The Spanish government said it is due to meet shortly to discuss what has happened.
Spanish Prime Minister Mariano Rajoy Brey said on Twitter: “To all administrations: the priority is to treat the wounded and aid the work of the security forces.”
The Foreign Office released a statement saying: “The British Embassy in Madrid and Consulate General in Barcelona are in contact with local authorities and urgently seeking further information following reports of an incident in central Barcelona.
“Local authorities have advised people to stay inside and stay away from the Las Ramblas area of the city. If you’re in the immediate area you should take care and follow the advice of the local security authorities.”