Four men arrested in connection with the deaths of 15 people in the twin vehicle terror attacks in Spain have appeared in court.

The accused - believed to be the only surviving members of a 12-strong suspected terror cell which is thought to have planned and executed the rampages in Barcelona and Cambrils - were brought to the High Court in Madrid.

The closed-door hearing comes a day after police shot and killed 22-year-old Moroccon-born Younes Abouyaaquob, suspected of driving a white Fiat van into crowds along Barcelona's famous Las Ramblas boulevard on Thursday.

13 people died, including a seven-year-old British-born boy.

Just hours later, a woman was killed in the seaside resort town of Cambrils, about 110 kilometres southwest of Barcelona, in an attempted repeat of the earlier crash. Five attackers were then killed in a shoot-out with police.

It later emerged that Abouyaaquob was also suspected of stabbing to death the driver of a car he hijacked while trying to evade capture by the authorities, bringing the death toll to 15.

A further 120 people were injured in the two attacks.

Among those in court on Tuesday was Driss Oukabir, whose passport was found in the abandoned van after the Barcelona attack.

He handed himself in to police, asserting his younger brother Moussa Oukabir, 17, who was killed in Cambrils, had stolen his documents.

Also in court was Mohammed Aalla, the alleged owner of the Audi A3 used in the Cambrils attack.

One of his brothers, Said, was killed in Cambrils and a second, Youssef, is believed by police to have died the day before the Barcelona attack in an explosion further down the coast at a house in Alcanar, about 80 kilometres southwest of Cambrils.

The house, dubbed a bomb-making factory, was allegedly used by those plotting the attacks.

Mohamed Houli Chemlal, who was detained after surviving the blast, was also in the dock.

The three were joined by Salah el Karib, who ran an internet cafe in Ripoll, about 100 kilometres north of Barcelona, where most of the suspects lived.

Meanwhile, reports that the Audi used in Cambrils had been photographed speeding in Paris some time before the attacks, were confirmed by the French interior minister.

Gerard Collomb told BFM-TV: "This group came to Paris, but it was a quick arrival and departure."