The number of British citizens killed while fighting with the terrorist organization PKK/YPG has reached seven, with the death of 24-year old Oliver Hall.
Hall was killed in a mine-sweeping operation in Syria's Raqqah city on Nov. 25, according to the BBC.
The PKK has been proscribed as a terrorist organization in the U.K. since 2001, however, the YPG is not on the list of banned organizations.
Jac Holmes (24), Mehmet Aksoy (32), Luke Rutter (22), Ryan Lock (20), Dean Carl Evans (22) and Konstandinos Erik Scurfield (25) were previously killed while fighting for the PKK/YPG.
The British authorities have said their citizens who joined armed groups in Syria could be questioned under anti-terrorism laws upon their return to the U.K.
Aiden Aslin (23) was taken into custody for questioning in September after returning to the country from the terrorist PKK/YPG in Syria.
The Henry Jackson Society, a London-based think tank, suggested in a report in August that the YPG should be proscribed in the U.K., after profiling 60 foreigners who joined the terrorist organization from 12 different countries.
"The Forgotten Foreign Fighters: The PKK in Syria" laid bare the ties between the PKK, which is listed as a terrorist organization in the EU and U.S. as well as Turkey, and the PKK/PYD in Syria.
It urged the U.K. government to distance itself from the PKK/PYD as it could potentially cause a crisis within Turkey -- a fellow NATO member.
It recommended the U.K. government "consider updating the Foreign Enlistment Act to prevent Britons from joining non-state actors engaged in conflict abroad".
Those who returned from the PKK/PYD "should be screened to assess if they require any further state attention, either from the criminal justice system or social services," the report read.
The PKK has waged a terror campaign against Turkey for more than 30 years that has led to the deaths of more than 40,000 people. It is a designated terror group in Turkey, the U.S. and the EU.
