Authorities are looking for 22-year-old Younes Abouyaaqoub, who they believe was behind the wheel of a van which left a trail of dead and injured on Barcelona's famed boulevard.

A man reacts at an impromptu memorial where a van crashed into pedestrians at Las Ramblas in Barcelona, Spain August 21, 2017.
A man reacts at an impromptu memorial where a van crashed into pedestrians at Las Ramblas in Barcelona, Spain August 21, 2017. (Reuters)

Spanish police on Monday extended the search for the driver behind the Barcelona attack to all of Europe as details emerged of how he fled on foot through the streets of the old town before disappearing.

The death toll in Spain's terror attacks rose to 15, Catalonia's regional minister Joaquim Forn told reporters on Monday, as a victim found stabbed dead in a car in Barcelona was linked to the case.

"We are raising the number of victims from 14 to 15 to include the victim in the vehicle found in Sant Just," he told journalists.

Authorities are looking for Younes Abouyaaqoub, a 22-year-old Moroccan-born man, who they believe was behind the wheel of a van which left a trail of dead and injured on Barcelona's famed boulevard.

The Catalan regional government said all European police forces were now searching for Abouyaaqoub and authorities could not rule out that he had slipped across the border into France.

"This person is no longer just being sought in Catalonia but in all European countries, this is an effort by European police," Joaquim Forn, in charge of home affairs in the northeastern Spanish region, told Catalan radio.

Forn confirmed that police were now almost certain Abouyaaqoub was the driver.

"Everything points to that," he added.

Authorities have stepped up checks at Spain's borders.

They also raided more homes overnight in Ripoll, a town in the foothills of the Pyrenees and close to France where many of the suspects in a 12-strong cell, thought to be behind the Daesh-claimed attack, had lived.

Others thought to be part of the Daesh have been arrested, shot by police or killed in an explosion at a house in Catalonia a day before Thursday's van attack.

The attack in Barcelona was linked to another hours later in the resort down of Cambrils, further down the Mediterranean coastline from Barcelona.

A car crashed into passers-by there and attackers got out to try and stab people. Five suspects were shot dead, while a Spanish woman died in the attack.

Abouyaaqoub abandoned the van after zig-zagging down Las Ramblas avenue at high speed, police have said. Witnesses had seen him walking away unarmed from the scene, they said.

Spanish papers El Pais and La Vanguardia said they had seen images of the man leaving Las Ramblas then crossing through La Boqueria food market, another tourist attraction, before disappearing.

El Pais published CCTV footage on Monday of a man wearing a black and white shirt similar to the one Abouyaaqoub wore when he was caught on a bank security camera the night before the attacks.

Spanish political leaders from all the main parties were also due to meet later on Monday to review security measures as part of cross-party efforts to unite on anti-terrorist efforts.

Source: Reuters