Thirteen people were confirmed dead and more than 100 others injured, in the Barcelona terror attack, a Spanish official said. Picture: Xinhua/Ying Qiang

Barcelona - A van on Thursday mowed down pedestrians on Las Ramblas, one of Barcelona's busiest streets, in what police said was "obviously a terrorist attack." 

Hours later police said they had responded to a second suspected terrorist attack in the town of Cambrils, 120 kilometres south of Barcelona.

WHAT WE KNOW

- At least 13 people were killed in the Barcelona attack and around 100 people were injured.

- Two men were arrested in connection to the attack: a Moroccan and a Spanish national from the North African Spanish enclave of Melilla.

- Police have launched a manhunt for a third man believed to have been the driver of the van.

- The Islamic State terrorist group said its "soldiers" were responsible.

- Police said an explosion that killed one person and destroyed a house Wednesday night in the town of Alcanar, 200 kilometres south of Barcelona, was "clearly" linked to the attack.

- Police said they had killed four suspects and injured a fifth while responding to the suspected terrorist attack in Cambrils

WHAT WE DO NOT KNOW

- It wasn't immediately clear if the incident in Cambrils was connected to the Barcelona attack.

- Police said that so far there was no evidence that an incident in which police shot dead a man who tried to evade a checkpoint, while leaving Barcelona hours after the attack, was connected to what happened on Las Ramblas.