Cambrils attack: Single Catalan police officer shoots dead four terrorists after Barcelona rampage

'To kill four people, even if you are a professional, is not easy to digest,' says regional official

Spanish police inspect a car after suspected terrorists knocked down six civilians with their car at Paseo Maritimo in Cambrils (EPA)

A single Catalan police officer shot dead four of the five terrorists killed in the wake of the Barcelona attacks.

The officer, reportedly from the Mossos d'Esquadra regional force, responded after the terrorists' car smashed through a roadblock in Cambrils and seriously injured another officer, according to La Vanguardia.

Catalan regional police official Josep Lluis Trapero said it was "not easy" for the officer involved despite being a professional.

A total of five suspects were killed after the Cambrils attack in which a car ploughed into a crowd, killing a woman, at about 1am on Friday.

The fifth terrorist was killed by a sergeant from a separate force, La Vanguardia reported, after he fled the scene. Suicide vests worn by the gang turned out to be fake.

The combined death toll from the Cambrils and La Rambla attacks has reached 14, authorities said on Friday.

People from 34 countries are among the dead and injured. The US State Department said at least one of those killed was an American citizen.

Four suspects have been arrested as police investigate an alleged cell of up to 12.

The manhunt is focusing on Moussa Oukabir, 18, the younger brother of one of the detained men.

His sibling, Driss, 28, handed himself into police in the town of Ripoll and claimed the younger man had stolen his identity documents in order to rent the van used to mow down pedestrians in central Barcelona.

Police are linking the Cambrils and La Rambla attacks as well as a house explosion in Alcanar on Wednesday.

Isis claimed responsibility for the killings.

Additional reporting by agencies