Responding to a parliamentary question on Friday, Justice minister Félix Braz (Déi Gréng), the prime minister, Xavier Bettel (DP) and foreign affairs minister Jean Asselborn (LSAP) confirmed the information but did not say whether the individual was in Syria or Iraq or held in a Kurdish prison.

The question comes as the caliphate in Syria and Iraq has been reduced by a US-led coalition to a handful of streets in Baghuz, in eastern Syria, where hostages are being held.

UN figures suggest that at its height, some 40,000 foreign fighters from 110 countries travelled to Syria and Iraq to join terror groups. In total some six are thought to have been Luxembourg residents.

Some have been killed in combat, while others left voluntarily after the start of the fall of Islamic State. According to MP Laurent Mosar (CSV), who asked the parliamentary question, some 900 foreign fighters are currently being held in Kurdish prisons.

In recent weeks European countries have been forced to reflect on how to manage these former fighters, some of which are women and began families while abroad. The UK, for instance, revoked the UK citizenship of teenager Shamim Begum, who joined Islamic State in Syria when she was 15.

The three Luxembourg ministers do not name the former Luxembourg resident still thought to be abroad but pointed out that they are not a Luxembourg national. In this instance, Luxembourg would not offer consular assistance. A Jihadi fighter coming to Luxembourg would be subject to monitoring and likely criminal sanctions.

Other media, meanwhile, have suggested it might be Steve Duarte, a Portuguese national who grew up in Luxembourg, and joined Islamic State group in Syria in 2014.