Updated

Families of those killed by a neo-Nazi group that sought to terrorize migrants in Germany called Tuesday for the investigation into the case to continue, even as the trial of its only known surviving member and four supporters draws to a close this week.

Campaigners and lawyers for the relatives claim there is compelling evidence the National Socialist Underground — suspected of 10 killings and at least two bomb attacks — had a wider network of supporters than authorities have acknowledged, including people who were paid informants for the German security services.

The case sent shockwaves through German society at a time when many believed the country was slowly accepting its migrant population. It has gained additional significance with the rise of the far-right Alternative for Germany party in recent years. The party has taken a strong anti-immigration line, railing against refugees and questioning whether even second- and third-generation immigrants truly belong to German society.

The National Socialist Underground, or NSU, operated in secret for almost 14 years before two of its three core members died in an apparent murder-suicide in 2011. A claim of responsibility subsequently mailed to media by Beate Zschaepe, now on trial in Munich, exposed myriad mistakes by investigators, who had long ruled out a far-right motive and instead suspected the migrants of being involved in organized crime, prompting accusations of institutional racism from human rights groups ,

"The NSU killed my father. The investigators took his honor," said Gamze Kubasik, the daughter of Mehmet Kubasik, a Turkish-born man who was shot dead in his convenience stall in the western city of Dortmund on April 4, 2006.

Seven other men of Turkish origin, a Greek man and a German policewoman were also killed by the group between 2000 and 2007.

Kubasik told reporters that she and other relatives had hoped for "100-percent clarity" when the trial began five years ago.

"Now there's a big hole inside of me," she said.

Among the key questions families had hoped the trial would reveal was why their relatives were targeted, said Abdulkerim Simsek, son of Enver Simsek, who died two days after being shot at his flower stall in Nuremberg on Sept. 9, 2000.

"Why did the killers choose my father," Simsek said. "I can't and won't believe that it was chance."

Lawyers representing the families as plaintiffs in court, as allowed under German law, say the wide geographical distribution of the victims suggests the NSU received information from local contacts in the cities where the killings were carried out.

In one case, an employee of the country's domestic intelligence agency was inside an internet cafe when the owner was gunned down, but claimed not to have seen or heard anything untoward.

After the NSU was exposed, a string of mistakes by Germany's many federal and state-level security agencies also came to light, including the fact that paid informants with codenames such as "Primus," ''Piatto" and "Corelli" were close to the group for years.

Chancellor Angela Merkel publicly apologized to the victims and their families, pledging that authorities would "do everything to investigate the murders, uncover those who helped and back them, and ensure the perpetrators get their just punishment."

Sebastian Scharmer, a lawyer for the Kubasik family, accused federal prosecutors of dragging their feet in the investigation, thereby allowing "crude conspiracy theories" to flourish.

A spokeswoman for the Federal Prosecutors Office, Frauke Koehler, said that nine people were still being investigated, but it's unclear whether any of them will be charged.

Scharmer said he feared a group like the NSU could strike again, despite Zschaepe's likely life sentence Wednesday and the death of her two alleged accomplices, Uwe Boehnhardt and Uwe Mundlos.

"It could happen again at any moment, if it's not already happening," he said.

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