Footage has emerged showing three terrorists who were killed in Spannish town of Cambrils laughing and joking with each other at a shop hours before they were shot dead by police.

Three of the terror cell responsible for killing 15 people in the seaside town and Barcelona were seen buying eggs, bread and lighters at a motorway service station near Cambrils on the day of the double terror attack.

The footage, obtained by Catalan newspaper, Ara, shows Omar Hychami, Houssaine Abouyaaqoub and Moussa Oukabir making one of several trips to the station before they were later killed by police after the second terror attack in Cambrils.

The attack, which occurred hours after a car ploughed into people on Barcelona's Los Ramblas, saw another vehicle drive into a crowd of people, killing one and injuring several others including a police officer.

The men then came out of the black Audi armed with machetes and axes. It later emerged that four of the five terrorists killed in Cambrils were shot dead by a single police officer.

It is believed the attack in Cambrils took place after the terrorist's original plan to target Barcelona attractions with home-made bombs fell through after an explosion at their 'bomb-making factory' at a house in Alcanar.

The explosion, which killed the terror cell's ringleader Imam Abdelbaki Es Satty, occurred at the house which contained more than 100 tanks of butane gas and materials to make TATP, an explosive dubbed the "Mother of Satan" which is frequently used in attacks by Islamic State militants.

Elsewhere, the region of Catalonia has announced an increase in security in Barcelona and other tourists landmarks in the wake of the attacks.

The installation of bollards to prevent further car attacks and an increase in police around transport stations are some of the measures to be imposed.

Joaquin Forn, who is in charge of home affairs in Catalonia, told reporters at a news conference: "We're looking at introducing (street) obstacles that could be mobile."

Forn added some permanent barriers may also be installed, as well turning some streets into pedestrian-only thoroughfares.