The German government on Monday admitted gross failures by the security services in dealing with a new brand of far-right \"terrorism\" after revelations of a decade-long killing spree by neo-Nazis. Interior Minister Hans-Peter Friedrich said it was still unclear whether a small group of extremists who admitted gunning down nine businessmen of foreign origin and a policewoman had a larger network behind them. \"It is deeply troubling that there was no connection made between the murder series across Germany and the far-right scene in Thuringia,\" the east German state where the group was based, Friedrich told the daily Bild. \"State interior ministers are calling for better coordination between police and domestic intelligence on the state level. I strongly back that.\" Federal prosecutors launched the probe last week after the discovery of a pistol used in the murder of the nine people in the home of a 36-year-old woman, Beate Zschaepe, a self-confessed neo-Nazi. Wanted by police for questioning over an armed robbery in the eastern city of Jena on November 4, she had turned herself in after blowing up a rented flat in the eastern town of Zwickau. Two suspects in the Jena robbery, who were close to Zschaepe in the neo-Nazi scene, were found dead in a caravan shortly afterwards. Investigators believe the two committed suicide. It was inside the caravan police found another firearm, that of the policewoman killed by a shot to her head in the southern town of Heilbronn in 2007. In a chilling DVD left behind by the two men, Uwe Mundlos, 38, and Uwe Boehnhardt, 34, they admitted to the unsolved murders of eight businessmen of Turkish origin and a Greek between 2000 and 2006 as well as the policewoman. News weekly Der Spiegel said they also admitted in the video to a nail bomb attack against Turkish immigrants in Cologne in which several were injured. A judge issued a detention order for Zschaepe late Sunday. Newspapers splashed a front-page picture of the unassuming woman with her auburn hair tied back in a ponytail wearing a pair of blue-tinted eyeglasses. She has reportedly refused to speak to police until she wins an agreement for a lesser sentence in return for a full confession. Bild reported that the killers had shot many of their victims in the face at point-blank range and even filmed their bloodied bodies as trophies. On Sunday, police arrested a 37-year-old alleged accomplice identified only as Holger G. \"There is no doubt this represents a new dimension of far-right violence which is why federal prosecutors are investigating accusations of formation of a terrorist organisation,\" Friedrich said. \"The probe by the federal prosecutor\'s office and federal police will quickly determine whether the three known perpetrators have a larger network behind them.\" Media at the weekend speculated about the formation of a \"Brown Army Faction\" of violent extremists -- a far-right version of the now-defunct far-left Red Army Faction that killed more than 30 people between the 1970s and 1990s. Chancellor Angela Merkel expressed shock over the crimes and pledged that German authorities would track down all those responsible. The head of the Central Council of Muslims in Germany, Aiman Mazyek, said the problem of far-right \"terrorism\" had been \"chronically underestimated\" in Germany while the focus was on Islamic militants, in the daily Neue Osnabruecker Zeitung. About three million people of Turkish origin live in Germany. Friedrich had warned after the killing of 77 people in Norway by right-wing extremist Anders Behring Breivik in July that Germany\'s far-right scene was also violent and dangerous. He told Bild that despite fervent speculation, there was no evidence to indicate that any of the three had been working as informants for the intelligence services. However Bild quoted investigators as saying Zschaepe had repeated contact with state intelligence agents from 1998 as part of a bid by authorities to infiltrate the neo-Nazi scene.