German police are investigating reports that guards at three asylum centres in North Rhine-Westphalia have been abusing the refugees interned in the centres. Photos released showing the abuse have been compared to Abu-Ghraib, whilst a colleague has told German media that the group of guards were nicknamed “the SS”, The Local has reported.

The abuses first came to light in Burbach, when a video which showed a refugee being forced to lie on a vomit-soiled mattress was found. A police investigation into the matter then uncovered a Whatsapp conversation on a the security guard’s phone, which included a photo of a refugee tied down by two guards, one of whom has his boot on the man’s neck. The guards, aged 26 and 30 were found by police to have criminal records for offences including assault, drugs and fraud.

As the investigation became more widespread, further examples of abuse were revealed including two guards in Essen who stand accused of assault for beating refugees, and in Bad Berleburg, where two more guards are being investigated for causing grievous bodily harm to a refugee in their care. In total, eleven guards across three centres are now under investigation.

The images have caused outrage across Germany. Focus Online said the images called to mind pictures released from the Abu-Ghraib prison in Iraq were US Army and CIA personnel tortured the prisoners.

Other news outlets have turned their ire on the state’s interior ministry, and its minister Ralf Jäger. “That something has gone wrong in what is the interior minister’s area of responsibility has become brutally clear since the weekend,” the Rheinische Post told its readers.

Germany is due to take in 200,000 refugees this year, up tenfold since 2007, and pressure is mounting as the government struggles to contain them all. Some have been housed in converted shipping containers; others in former barracks, whilst in Cologne an empty DIY store has been allocated as housing space.

“We must step away from closed accommodation. It is inhumane and opens the door for misuse of authority,” Bernd Riexinger, leader of the left wing party Die Linke told Spiegel Online. Katrin Göring-Eckardt, leader of the Green party in the Bundestag has called for a “national refugee summit”, telling the Rheinische Post “The rapid increase in the number of refugees has been evident for years. The government’s lack of action is now coming back to bite.” She would like to see all of the political parties, federal, state and local politicians, and representatives from refugee organisations all coming together to discuss the subject properly.

Meanwhile, as investigations continue more abuses – and the lack of due diligence being undertaken by security companies when hiring guards – are being brought to light. A guard at the Burbach refugee centre has spoken anonymously to local paper the Siegerlandkurier, telling of the “legal vacuum” that existed in the centre.

He described an environment in which guards were overworked, and refugees systematically abused, adding that some of this colleagues clearly had nationalist political leanings. He also described how the group of guards that he worked with were nicknamed “the SS” (after Hitler’s storm troopers), thanks to their habit of scouring the centre for refugees breaking rules on drinking and smoking.

He alleges that the guards also had a “problem room” for refugees who were difficult to deal with, in which they were placed for up to eight hours a day with no access to toilet facilities. The room contained only a mattress.

The state premier Hannelore Kraft has said that she is “dismayed” and “ashamed” at what has taken place. Ralf Jäger has responded by announcing that in the future all security guards applying to work at refugee centres will have to be approved by police, and the Federal Office for the Protection of the Constitution (BfV). “Criminals are at work,” he said.