A cell of suspected right-wing extremists operating within the German army are being investigated as the probe into an alleged terror plot widens.

Prosecutors are investigating a group of up to five people surrounding a soldier accused of posing as a Syrian refugee to carry out a “false flag” attack.

The suspect, named only as Franco A, was arrested after police traced a loaded gun he stashed at Vienna International Airport but investigations at his barracks have revealed signs of a wider network.

An assault rifle case carved with a swastika was found in his room, where the letters HH [Heil Hitler] were inscribed on the wall and a Nazi-era pamphlet depicting a Wehrmacht soldier was discovered.

Germany’s RND media group published photos of the evidence, which forms part of a report drawn up by the ministry of defence.

Gerd Hoofe, the defence secretary, said there were also “indications of possible ammunition loss or theft” at Franco A’s barracks in Illkirch-Graffenstaden, France.

He did not raise any alarm over extremism in the army, despite writing a master’s thesis on “political change and subversion strategy” at a French university in 2014 that was found to contain far-right thinking.

German defence minister Ursula von der Leyen is to visit Illkirch barracks in France during investigation to an alleged far-right terror cell in the German army (EPA)

Franco A appeared at his barracks on time and completed all courses, even while dashing back to Bavaria to collect welfare payments as part of his double life as a refugee.

The lieutenant registered in Giessen, Hesse, on 30 December 2015 – as Germany was overwhelmed by the arrival of almost a million asylum seekers - then submitted an asylum application at Zirndorf in Bavaria in January last year.

He created a fake persona under the name David Benjamin, telling immigration officials he was a Damascus fruit seller from a Christian family with French roots, German media reported.

No doubts appear to have been raised over the credibility of the 28-year-old’s background, despite him speaking mainly French with a smattering of Arabic from a language course.

The ruse was only discovered when Franco A was arrested in Austria after returning to retrieve an unregistered 7.65mm pistol from a toilet at Vienna International Airport in February.

A fingerprint check revealed his fake identity as a Syrian refugee, but when “David Benjamin” failed to answer a court summons in Austria, a wider investigation was triggered.

He had a list of five potential targets for the attack, the Tagesspiegel newspaper reported, including former President Joachim Gauck, justice minister Heiko Maas, a prominent left-wing politician and the Berlin Center for Political Beauty.

If the plan had succeeded, his fingerprints would have registered on the refugee records system and led investigators to his false identity as a Syrian asylum seeker, turning fresh scrutiny on migrants in Germany.

“These findings, as well as other evidence, point towards a xenophobic motive for the soldier’s suspected plan to commit an attack using a weapon deposited at Vienna airport,” prosecutors said.

Refugees settle in Germany Show all 12 1 /12 Refugees settle in Germany Refugees settle in Germany Germany Mohamed Zayat, a refugee from Syria, plays with his daughter Ranim, who is nearly 3, in the one room they and Mohamed's wife Laloosh call home at an asylum-seekers' shelter in Vossberg village on October 9, 2015 in Letschin, Germany. The Zayats arrived approximately two months ago after trekking through Turkey, Greece and the Balkans and are now waiting for local authorities to process their asylum application, after which they will be allowed to live independently and settle elsewhere in Germany. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity 2015 Getty Images Refugees settle in Germany Germany A refugee child Amnat Musayeva points to a star with her photo and name that decorates the door to her classroom as teacher Martina Fischer looks on at the local kindergarten Amnat and her siblings attend on October 9, 2015 in Letschin, Germany. The children live with their family at an asylum-seekers' shelter in nearby Vossberg village and are waiting for local authorities to process their asylum applications. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity Getty Images Refugees settle in Germany Germany Kurdish Syrian asylum-applicant Mohamed Ali Hussein (R), 19, and fellow applicant Autur, from Latvia, load benches onto a truckbed while performing community service, for which they receive a small allowance, in Wilhelmsaue village on October 9, 2015 near Letschin, Germany. Mohamed and Autur live at an asylum-applicants' shelter in nearby Vossberg village. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity Getty Images Refugees settle in Germany Germany Mohamed Ali Hussein ((L), 19, and his cousin Sinjar Hussein, 34, sweep leaves at a cemetery in Gieshof village, for which they receive a small allowance, near Letschin Getty Images Refugees settle in Germany Germany Mohamed Zayat, a refugee from Syria, looks among donated clothing in the basement of the asylum-seekers' shelter that is home to Mohamed, his wife Laloosh and their daughter Ranim as residents' laundry dries behind in Vossberg village on October 9, 2015 in Letschin, Germany. The Zayats arrived approximately two months ago after trekking through Turkey, Greece and the Balkans and are now waiting for local authorities to process their asylum application, after which they will be allowed to live independently and settle elsewhere in Germany Getty Images Refugees settle in Germany Germany Asya Sugaipova (L), Mohza Mukayeva and Khadra Zhukova prepare food in the communal kitchen at the asylum-seekers' shelter that is their home in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Efrah Abdullahi Ahmed looks down from the communal kitchen window at her daughter Sumaya, 10, who had just returned from school, at the asylum-seekers' shelter that is their home in Vossberg Getty Images Refugees settle in Germany Germany Asylum-applicants, including Syrians Mohamed Ali Hussein (C-R, in black jacket) and Fadi Almasalmeh (C), return from grocery shopping with other refugees to the asylum-applicants' shelter that is their home in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Mohamed Zayat (2nd from L), a refugee from Syria, smokes a cigarette after shopping for groceries with his daughter Ranim, who is nearly 3, and fellow-Syrian refugees Mohamed Ali Hussein (C) and Fadi Almasalmeh (L) at a local supermarket on October 9, 2015 in Letschin, Germany. All of them live at an asylum-seekers' shelter in nearby Vossberg village and are waiting for local authorities to process their asylum applications, after which they will be allowed to live independently and settle elsewhere in Germany 2015 Getty Images Refugees settle in Germany Germany Kurdish Syrian refugees Leila, 9, carries her sister Avin, 1, in the backyard at the asylum-seekers' shelter that is home to them and their family in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Somali refugees and husband and wife Said Ahmed Gure (R) and Ayaan Gure pose with their infant son Muzammili, who was born in Germany, in the room they share at an asylum-seekers' shelter in Vossberg village on October 9, 2015 in Letschin, Germany. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity, and are waiting for authorities to process their application for asylum 2015 Getty Images Refugees settle in Germany Germany German Chancellor Angela Merkel pauses for a selfie with a refugee after she visited the AWO Refugium Askanierring shelter for refugees in Berlin Getty Images

A 24-year-old student suspected of being an accomplice in the plot, Mathias F, has also being arrested, with explosives found at his home.

Germany’s federal prosecutor’s office has taken over the terror investigation, which has sparked probes in the office for migration, interior ministry and military.

Ursula von der Leyen, the defence minister, cancelled a scheduled visit to the US on Tuesday and summoned military commanders to discuss the plot and other recent scandals including sexual abuse and hazing at another military base.

After attacking “weak leadership” she ordered the most senior 100 generals and admirals to attend a meeting in Berlin on Thursday.

“We have to ask systematically how someone with such clear right-wing extremist views, who writes a master's paper with clearly nationalistic ideas ... could continue to pursue a career in the Bundeswehr,” Ms von der Leyen told reporters.

She plans to travel to Illkirch for an update on the investigation as some politicians pushed back against her criticism of the military.

Henning Otte, a fellow member of Angela Merkel’s conservative CDU/CSU lawmaker and head of the parliamentary defence committee, told Reuters the military had “no fundamental problem with radicalism or abuses”.

But Germany's military intelligence agency has recorded 275 suspected case of right-wing extremists in the military's ranks, including some dating back to 2011 and 53 cases first identified this year.