Two brothers are among those suspected of being involved in the Spain terror attacks in Barcelona and Cambrils which left 14 dead and 130 injured.

Moussa Oukabir, thought to be 17 or 18 years old, and Driss Oukabir, in his 20s, have been widely linked to the twin atrocities in the popular tourist destinations.

But details of their alleged roles, the identity of the driver of the van and the number of attackers involved remain unclear.

El Pais said police are hunting for Moussa Oukabir, who is suspected of using his brother’s documents to rent the van which ploughed through crowds on Las Ramblas.

It has been reported that the teenager said on social network Kiwi that he would kill non-Muslims if he ruled the world for the day.

His older brother, Driss Oukabir, was said to have been arrested in the hours following the Barcelona rampage.

Flowers, messages and candles form a memorial tribute to the victims on Barcelona's historic Las Ramblas promenadeFlowers, messages and candles form a memorial tribute to the victims on Barcelona’s historic Las Ramblas promenade (Manu Fernandez/AP)

According to reports, he told police he was not involved and his documents were stolen.

It is not yet clear if Moussa Oukabir was behind the wheel of the Barcelona attack vehicle, but officials have said that one of five terrorists killed by police may have been the driver.

Four people, aged 21, 27, 28 and 34, have been arrested in connection with the attack, police said.

Three are Moroccan and one is Spanish, and none of them were previously known to security services for terror-related reasons.

The five terrorists killed have not been identified by authorities.