Over a dozen people had been killed, including foreign nationals, and many other injured as a van crashed into a crowd in the center of the Spanish city of Barcelona.
On its Twitter account, city police described the incident as a "massive crash," in a statement released on Thursday, saying, "Huge collision on Las Ramblas in Barcelona by an individual driving a van, many injuries."
Conflicting reports had been so far released on casualties following the attack.
Cadena Ser radio, citing police sources, said at least 13 people had been killed in the attack, which has been called a terrorist attack by police in Barcelona.
Other media including El Pais said there were at least 10 dead. A police spokeswoman could not immediately confirm the number of casualties.
Catalan police, however, said at least one person has been confirmed dead and 32 people injured following the attack, adding that 10 of those injured are in serious condition.
Hours after the attack, a Catalan government official said that there were 13 dead and around 100 injured in the attack.
Later on Thursday night, the Wahhabi Daesh [Arabic acronym for "ISIS" / "ISIL"] terrorist group claimed responsibility for the deadly attack on its Amaq propaganda website.
The Spanish police noted that they were clearing the area after the incident, which has left a number of people injured.
The area around the incident was cordoned off, with several ambulances and police vehicles on the scene, an AFP correspondent said.
Barcelona's emergency services asked people not go to the area around the city's Placa Catalunya, requesting the closure of nearby train and metro stations.
A report by El Pais newspaper stated that the driver of the vehicle had fled on foot after mowing down dozens of people.
The El Periodico newspaper report indicated that two armed men had entrenched themselves at a bar in Barcelona's city center after the van incident, noting that it was not immediately clear if the men were the drivers of the van.
A Spanish police source initially noted that a person suspected of driving the van into pedestrians was holed up at a bar.
The unnamed source said, "One of the attackers is holed up in a bar," adding that police were looking for a total of two suspects.
Catalan police, however, later announced that there was nobody holed up in the bar, adding that they had arrested two men linked to Barcelona van attack.
Meanwhile, Catalan police said on Twitter that they shot dead a driver of a vehicle that ran over two police officers at a checkpoint in Barcelona following the van attack in the city center. Spanish media had earlier reported that at least one policeman was injured at the checkpoint.
It was not immediately clear whether the incident was linked to the first attack in Las Ramblas avenue.
Within hours of the attack, Driss Oukabir, a 28-year-old man of Moroccan origin whom police said had rented the van used in the attack, reportedly turned himself in after seeing his photo being circulated online, claiming his documents had been stolen.
But Lluis Trapero of the regional police of Catalonia said the driver of the van that mowed into the packed street was still on the run, adding that two other suspects - a Spaniard and a Moroccan - had been arrested.
Following the incident Spain's Prime Minister Mariano Rajoy said he was in contact with authorities, adding on Twitter that the priority was to attend to the injured.
Police in Barcelona have announced that they are dealing with a "terrorist attack," adding that they are searching for driver of the van.
Later reports indicated that a second van linked to Thursday attack in Barcelona had been found in the small town of Vic in Catalonia. The city council said that police had cordoned off the area and were inspecting the vehicle.
In another attack just a few hours after the Barcelona rampage, six civilians and a policeman were injured after an assailant rammed his car into a crowd of people in the resort town of Cambrils, south of Barcelona.
Police initially said they had killed four "perpetrators" and injured another during an operation against the "terrorist attack" in Cambrils in the early hours of Friday morning. They later said the fifth suspect died of his wounds.
Police officials also said a blast that killed a person and injured several others at a house in Alcanar Platja on Thursday morning was linked to the Barcelona attack.
Rajoy told reporters late on Thursday night that the country is "united in grief" after the terrorist attack in Barcelona.
"Today the fight against terrorism is the principal priority for free and open societies like ours. It is a global threat and the response has to be global," he told a news conference in Barcelona.
The prime minister added that he would ask Spain's other political parties to reaffirm its anti-terrorism pact.
Various European cities had already seen terrorist attacks on pedestrians mostly carried out by Daesh operatives using various kinds of vehicles as weapon.
Source: News Agencies, Edited by website team