An IS network had planned to attack crowded public places in Spain's second city in September 2015 but was disrupted by the arrest of the operative at the centre of it, Moroccan national Abdeljalil Ait el-Kaid, according to the report published in CTC Sentinel, a US-based publication that researches militant affairs.
"Investigators have learned the disrupted plot to strike Barcelona was meant to be similar to the one later executed in Paris and was meant to also involve operatives from France and Belgium with whom el-Kaid was meant to link up with," it said.
"As with the Paris attacks, the Barcelona plan was to involve the use of Kalashnikov rifles and bombs in multiple crowded spaces such as concert halls, dining areas and sports events," it added.
The report, published in the January edition of CTS Sentinel, was prepared by two top researchers on global terrorism at the Real Institute Elcano, a Madrid think-tank.
“Spaniards, You Are Going to Suffer:” The Inside Story of the August 2017 Attacks in Barcelona and Cambrils. We suggest this analysis by @F_Reinares y @carolagc13 at @ctcwp #terrorism https://t.co/Py5DlbxgrX— Real Instituto Elcano (@rielcano) January 25, 2018
It was based on interviews with police, intelligence officers and judicial officials with knowledge of the case as well as judicial documents that are not subject to a gag order.
El-Kaid lived in Torrevieja on the Mediterranean coast of Spain until September 2014, when he left to join the Islamic State group in Syria.
There he allegedly joined the circle of Abdelhamid Abaaoud, the Belgian who allegedly led the cell that carried out the Paris attacks that killed 130 people.
El-Kaid was arrested in June 2015 in Warsaw, Poland while in transit from Istanbul on his way back to Spain on Abaaoud's orders to prepare the attack in Barcelona, according to the report.
This plot was not related to the attacks in Barcelona and the nearby seaside resort of Cambrils in August 2017 that killed 16 people, according to the researchers.
The only survivor among the 10 gunmen who carried out the killing spree in Paris on the night of November 13, Salah Abdeslam, is due to appear in court in Belgium early next month.
The heavily armed jihadists attacked the national stadium, bars and restaurants in the French capital as well as the Bataclan concert venue in a bloodbath claimed IS.