* Poll shows 74 pct in favour of banning NPD
* Police reopen cases with a possible racist motive
* Firearms, photos of NSU members shown to media (Adds poll, appeal, details of NPD, MP)
By Stephen Brown
BERLIN, Dec 1 (Reuters) - German police are investigating links between a neo-Nazi group that murdered nine Turkish and Greek immigrants and a far-right party with representatives in two state assemblies that could face a ban on its political activities.
Germany has more than 400 police and prosecutors looking into how the "National Socialist Underground" could have stayed undetected until November, when two members were found dead in a burnt-out mobile home and a third handed herself in to police.
The head of Germany's crime squad, Joerg Ziercke, said the arrest this week of a 35-year-old man in Jena in east Germany where the cell was based, indicated a link to the anti-immigrant National Democratic Party (NPD).
The man, named by the investigators as Ralf Wohlleben, was formerly a senior NPD official in the state of Thuringia. He is suspected of providing the group with weapons and ammunition.
"I am convinced we will find further links to the NPD," he told a news conference. "But it is up to politicians to decide what to do with the evidence found in our inquiries, that is not our job."
In a new poll for public broadcaster ARD, 74 percent were in favour of banning the NPD and 80 percent believed privacy laws should be changed to let security services keep data on people suspected of belonging to potentially violent right-wing groups.
Evidence displayed for the media included a dozen firearms and photos of NSU members Uwe Mundlos and Uwe Boendhardt -- police believe the former shot the latter, then killed himself.
They also showed photos of Beate Zschaepe, whom police say set the caravan and a nearby house on fire, possibly to cover up evidence of their latest bank heist.
The photos were from 1998 when the trio were in their early 20s, and were on show alongside neo-Nazi propaganda such as a red case with a large black-and-white swastika.
German police are embarrassed the NSU could have escaped detection for so long despite carrying out 10 murders between 2000 and 2007.
In the ARD poll, 81 percent agreed the state "often leaves the road open to neo-Nazis and right-wing extremists" while 58 percent thought the police and intelligence service "turn a blind eye" to the far-right.
Chancellor Angela Merkel has called the NSU's existence "a disgrace". Turkey has called on Germany to take seriously the racist threat to the 3 million Turks living here.
NETWORK FOR NEO-NAZIS
As well as the so-called "doner murders" -- a name attached by the media because some victims owned Turkish fast-food stands -- the NSU is suspected of crimes such as two bomb attacks in Cologne in 2001 and 2004, and 14 bank robberies when they got away with at least 600,000 euros (${esc.dollar}808,200), police said.
Ziercke said police had reopened all unsolved cases with a possible racist motive and had alerted 88 people identified as potential targets, including politicians and Muslim leaders, whose names were among thousands on DVDs seized by police.
Police are also probing what linked the group to a German policewoman whom they killed in 2007.
"The question is when, where, how and above all why did the policewoman get mixed up with these delinquents?" said Ziercke, launching an appeal to the public for clues about who had helped them get false documents and rent 56 vehicles from 2000-2011.
"We hope that by going public we will get clues from the population that would otherwise remain secret," he said.
Public interest has been sharpened by reports security services had informants among neo-Nazis and the NPD, which has condemned the crimes.
Represented in two state assemblies -- the east German states of Saxony and Mecklenburg-Vorpommern -- but not in the federal parliament, the NPD gets about 1 million euros in taxpayer funding a year.
The German intelligence agency describes the party as racist, anti-Semitic and inspired by the Nazis. Its local election campaigns blame immigrants for crime and unemployment and its supporters are mostly unemployed young men with little education in depressed areas of the east.
One attempt to ban the NPD failed in 2003 after witnesses were exposed as intelligence agency informants. But the head of parliament's interior committee, Wolfgang Bosbach from Merkel's conservatives, said there were now better grounds for a ban.
"If it is proved the NPD had contacts to this cell, it will be a strong argument for seeking a ban of the NPD," he said.
The centre-left opposition is also keen for a ban. Thomas Oppermann of the Social Democrats said it had been proven "that members of the NPD -- not just people now under arrest -- have provided a support network for the neo-Nazis".
(${esc.dollar}1 = 0.7424 euros) (Additional reporting by Diane Niedernhoefer; Editing by Sophie Hares)
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