At least 13 people have been killed and more than 100 injured after a van ploughed into pedestrians in a terror attack in a busy tourist area of Barcelona.
Of the 100 injured, Spanish emergency services have said 15 have serious injuries.
UPDATE 10pm: The two suspects in custody are a Spanish national from Melilla and a Moroccan but neither was the van driver, Catalan authorities said.
Officials are also linking the van attack to an explosion in Catalonia the previous day in which one person was killed.
UPDATE 9pm: Unconfirmed local reports suggested an attacker had been shot by police on the outskirts of the city.
Police also said a driver had run over two police officers in a town north of the city, but it was not clear if this was related to the attack.
A Belgian national is among the dead, Belgium's deputy prime minister Didier Reynders confirmed on Twitter.
UPDATE 8.45pm: The so-called Islamic State claimed responsibility for the attack in which a van ploughed into crowds in the Spanish city of Barcelona on Thursday, the group's Amaq news agency said.
"The perpetrators of the Barcelona attack are soldiers of the Islamic State and carried out the operation in response to calls for targeting coalition states," the agency said, referring to a United States-led coalition against the Sunni militant group.
The terror group has frequently declared that it was behind terrorist incidents in recent years, but experts have warned their claims should be treated with caution.
The terror attack - the deadliest on Spanish soil since more than 190 people died in the Madrid train bombs in 2004 - brought widespread condemnation.
Carles Puigdemont, the president of Catalonia, confirmed the two arrests at a press conference.
He also said 12 people were confirmed dead and at least 80 taken to hospital, which conflicted with interior minister Joaquim Forn, who said 13 people had died.
UPDATE 8.15pm: Two people have been arrested after the Barcelona van attack, Catalonia's regional president has said.
Meanwhile, the Taoiseach, Leo Varadkar TD, has expressed his abhorrence at the terrorist attack, saying: "On behalf of the Government and the Irish people, I would like to extend my deepest sympathy to Prime Minister Rajoy and the people of Barcelona and Spain following this callous act."
(Added 8.24pm:) President Michael D Higgins has said: "It was with great sadness that I learned of the tragic loss of life and the injuries that have taken place in Barcelona today.
"I have asked the Spanish Ambassador to convey my deepest condolences to the Government and people of Spain and to the Mayor of Barcelona...As President of Ireland I want to send the people of this great and welcoming city not only our sympathy but also the solidarity of the people of Ireland."
(Added 10.30pm): Justice Minister Charlie Flanagan has also responded to the attack.
"Today’s attack in Barcelona is an unspeakable act of terrorism. It is clear that the intention of those who carried out this appalling, evil act was to kill, wound and terrorise innocent people enjoying the freedoms we share and cherish. Our thoughts are with the victims and their families.
"All right-thinking people who value democracy stand in solidarity with the people of Spain in this time of anguish for them. We will not be defeated by barbarity. Our shared values of peace, tolerance and democracy will prevail in the face of terrorism."
Irish citizens in the vicinity of the incident are advised to follow the advice of local authorities. Anyone with concerns for the safety of loved ones in Barcelona can contact the Consular Assistance team in the Department of Foreign Affairs and Trade on 014082000 or the Irish Embassy in Madrid on 0034 914364093.
UPDATE 7.45pm: At least 13 people have died and more than 80 have been injured after a van ploughed into pedestrians in a terror attack in a busy tourist area of Barcelona.
Police have arrested a man after a white Fiat van tore through the Las Ramblas district which was packed with shoppers and holidaymakers.
Local media said police were hunting a man named Driss Oukabir who is suspected of having rented the van used in the attack.
The passport of a Spanish citizen, of Moroccan origin, was found at the scene.
The identity of the arrested man is not clear.
There were also reports that detectives believe two vans were used, one for the attack and a second as a getaway vehicle.
Initial reports suggested suspects had been holed up in a city centre bar surrounded by police, but authorities dismissed this saying there was no-one in the bar.
Facebook activated its Safety Check feature, which allows people in the aftermath of a disaster to tell friends they are safe.
UPDATE 6.50: Up to 13 people are feared dead and dozens more injured after a van ploughed into pedestrians in a terror attack in a busy tourist area of Barcelona.
The driver of a white Fiat van, who fled on foot after the incident in Las Ramblas, was reported by local media to have been holed up in a city centre bar surrounded by police.
But authorities said a suspected terrorist had been arrested and there was no-one in the bar.
Sources confirmed that the death toll from the latest terror attack to strike a major European city was expected to reach 13.
The passport of a Spanish citizen, of Moroccan origin, was found at the scene.
Catalonia's interior minister Joaquim Forn told reporters: "Unfortunately the number of fatalities will likely rise."
And a spokesman from the Barcelona Civic Protection Office said: "The official information I have is that we have one person dead, and 64 people were attended by medical services."
Dublin Live editor Alana Fearon has posted the below video from the site of the attack.
Ms Fearon is locked inside a restaurant on the Las Ramblas strip.
UPDATE 6pm: At least three people are feared dead and dozens injured after a van ploughed into pedestrians in a terror attack in a busy tourist area of Barcelona.
Police are hunting for the driver of a white Fiat van, who fled on foot after the attack in Las Ramblas.
According to unconfirmed reports, the death toll could be as high as 13 and two attackers are holed up in bar near the scene.
Government officials confirmed one fatality and said at least 32 people had been injured, seven of them seriously.
The vehicle careered into terrified pedestrians in the busy tree-lined promenade, one of the most popular parts of the city, visited by tourists and locals alike.
Estampida ahora mismo en El Corte Inglés de Plaza Catalunya en Barcelona pic.twitter.com/72LLRmJjRk— Jordi Perez Colome (@jordipc) August 17, 2017
UPDATE: Two people have been killed, and dozens of people have been injured in Barcelona after a van ploughed into pedestrians in a suspected terror attack.
There are also reports of two armed men entering a bar in the popular tourist city.
Witnesses reported gunshots and seeing people running away and screaming after the crash in the Las Ramblas area.
The van driver is reported to have fled the scene following the crash.
The El Periodico newspaper says the driver has been described as approximately 5ft 5" tall, dressed in a white shirt with blue stripes.
Police are reportedly negotiating with the alleged perpetrators, who have taken hostages at the Turkish restaurant La Luna in Istanbul, near the La Boqueria food market, where they have entrenched themselves.
Local media are reporting 13 casualties.
The Department of Foreign Affairs says it's monitoring developments in Barcelona closely.
Anyone with concerns for the safety of loved ones can contact the Consular Assistance team in the Department on 01-4082000 or the Irish Embassy in Madrid on +34 914364093.
Minister Simon Coveney said he is appalled by the incident and he wishes to convey his condolences and solidarity with the people of Spain at this time.
Lawyer and University of Glasgow rector Aamer Anwar was walking La Ramblas when he heard screaming.
He said a shopkeeper told him five or six people were badly injured and described the scene as "chaos".
Mr Anwar said: "I had been to the Cathedral and walking down Las Ramblas for something to eat. Part of it was in the shade so I decided to keep walking down and literally within 10 seconds there was a crashing noise.
"I turned around and people were screaming - I could see a woman screaming with her kids - people started running and jumping into shops. I ran for about 50 or 100 metres and stopped to see what was happening. The police were very quickly on the scene and getting people to move back.
"I could see chaos right at the top area and I spoke to a shopkeeper who had run down and was screaming. He was Bengali so I spoke to him in Urdu and he said a van had driven into a crowd and he thought there were five to six people very seriously injured."
EARLIER: Police in Barcelona say several people have been injured after a vehicle crashed into a crowd in Barcelona.
Police say a white van mounted the pavement and struck groups in the city's Las Ramblas district.
Catalan emergency services said people should not go to Placa Catalunya area.
They have also asked to close metro and trrain stations in the area close to the crash.
"It was quite terrifying... children were hysterical" - Eyewitness to the van crash in Barcelona describes what she saw pic.twitter.com/9twOKBzPFI— Sky News (@SkyNews) August 17, 2017
Local media is reporting that the driver of the van has fled the scene on foot.
VIDEO: White van in the Las Ramblas area in central Barcelona.August 17, 2017
Van crashes into crowds of peoples near Las Ramblas in Barcelona city centre - multiple injuries (Video - D Cohen) pic.twitter.com/mw6fpwWQto— BREAKING.UK (@BreakingDotUK) August 17, 2017