The Turin Prosecutor's Office in northern Italy requested "special surveillance" Tuesday for five Italian citizens who joined the PKK terrorist group's Syrian affiliate People's Protection Units (YPG) and returned to the country, saying the five citizens could pose a "societal threat."

In a written statement, the prosecutor's office requested special surveillance on the grounds that the five people had been working for the terrorist group for last two years and could present a societal threat due to the military training they received from the terrorist group in Syria.

The five Italians, who are members of an extreme left-wing group in Italy and will face trial on Jan. 23, "are not being investigated as terrorists," the statement said.

The five individuals confirmed to the Italian press that they received military training in Syria and argued that this training was necessary regarding the circumstances. They opposed the decision to place them under surveillance, saying the move "restricts their freedom."

Separately, another Italian citizen – 50-year-old Giovanni Francesco Asperti, who was also known to be a fighter for the YPG – was killed in a traffic accident in Syria's Deir el-Zour province on Dec. 7, as confirmed by Italy's Foreign Ministry. The ministry officials gave no further details about the subject.

The PKK – which is listed as a terrorist organization by Turkey, the U.S., the EU and NATO – has waged a decadeslong terror campaign against Turkey and is responsible for the deaths of nearly 40,000 people, including women and children. The YPG terrorists are the Syrian offshoot of the PKK who have been operating under an umbrella group, Syrian Democratic Forces (SDF) under the pretext of fighting against Daesh.

A 2017 Europol report on terrorism in the EU said that the PKK has recruited its members among the Kurdish community in Italy for activities in Europe and in conflict zones abroad. The report cited ongoing fundraising, propaganda and recruitment activities by the PKK in Italy, Belgium, France, Germany, Romania and Switzerland.