In a statement, national authorities said they carried out the police action here in Portugal, in the early hours of Sunday morning, responding “to a house search where the suspect was” to be found.


They did not, however, specify the exact location of the raid.


The defendant appeared in court on Monday and in view of the evidence presented by the authorities, was remanded in custody pending trial by the investigating judge.


Respected online newssite Diário de Notícias (DN) elaborated, stating the detainee is Portuguese and is understood to have helped the so-called ‘Leyton Cell’ in England, which comprised six suspected Portuguese jihadists from the Sintra area and was the target of criminal investigations by Portugal’s Public Prosecutor.


The ‘Leyton Cell’ encompassed brothers Celso and Edgar Costa; Sadjo Turé, Fábio Poças, Sandro Monteiro and Nero Saraiva.


Of those six, only the latter is reportedly still alive, although he is thought to have been seriously injured in Baghdad in an attack by allied forces.


Edgar and Celso moved to London in early 2000 and are believed to have been converted circa 2006.


In 2008 they are understood to have travelled to Morocco, where they lived for about six months. They would visit family in Sintra and return to Leyton, where, according to DN, they ran a network of young Muslim foreigners who wanted to enter ISIS ranks.


DN claims they eventually lived in Portugal for a while, with their newborn children and wives, before heading for Syria in 2013 to fight for Islamic State.


According to investigations by magazine Sábado and newspaper Expresso, the Costa brothers were considered “influential” in the hierarchy of the terrorist organisation.


Edgar is said to have gained military experience in Africa, where he joined a militia of the radical group Al-Shabaab in Somalia and Tanzania.


In March 2014, DN reports, Celso appeared on YouTube calling on Muslims around the world to enlist in ISIS. Last summer he appeared in three photos hugging Fábio Poças and Deso Dogg, a German rapper who became a member of Islamic State.


This week’s PJ operation, staged in an unspecified location in Portugal, was carried out by the PJ’s National Terrorism Combating Unit (UNCT), within the scope of an investigation spearheaded by the Central Department of Investigation and Criminal Action (DCIAP).


According to a joint statement from the PJ and the Attorney General’s Office, the action was staged “within the remit of a criminal investigation involving terrorist crimes, namely the involvement of national citizens in the ranks of the Islamic State”.


It elaborated that “the defendant has been living in the United Kingdom for several years, and from there he has carried out various activities for Islamic State, namely as a support and facilitator for the movement of other nationals to the territories of Iraq and of northern Syria”.


It stressed that an investigation in Portugal is still ongoing.