Berlin (AFP) - German prosecutors said Monday they suspect a far-right motive in the assassination-style murder of a pro-migrant city official that stunned the country two weeks ago.
This would make the night-time killing of Walter Luebcke, 65, with a close-range gun shot to the head "a political assassination," they said.
Chancellor Angela Merkel described the development as "depressing".
"I hope we'll soon have clarity," Merkel said during talks with labour unions and employee organisations in Berlin.
It was "right and proper that all the information be investigated as quickly as possible," the Chancellor said.
A man in custody, identified only as 45-year-old Stephan E., is believed to have killed Kassel city administration chief Luebcke on June 2, federal prosecutors said.
"There is sufficient evidence pointing to a right-wing extremist background to the crime," said the prosecutors' statement, citing "the life history of the accused, and his publicly expressed opinions and views".
Investigators were looking into possible co-conspirators but so far had "no evidence that the accused was part of a terrorist network," they said.
Luebcke, of Chancellor Merkel's conservative Christian Democrats, was shot dead in the early hours of June 2 on the terrace of his home near Kassel, 160 kilometres (100 miles) northeast of Frankfurt.
At the height of Europe's 2015 mass refugee influx, he had passionately spoken out in defence of migrants, drawing the fury of the far right for telling xenophobes that they "could leave Germany".
Since his death, hundreds of posts from social media accounts tied to right-wing extremists have hailed his murder, in turn drawing strong condemnations from President Frank-Walter Steinmeier and other politicians.
Justice Minister Katarina Barley said she was horrified not just by the "unspeakable crime" but also by the "online agitation, the threats and finally -- after his death -- the mockery of Walter Luebcke".
- Pipe-bomb attack -
Stephan E., reportedly a married father of two, was arrested Saturday by police commandos in Kassel, Hesse state, on the basis of DNA evidence.
On Monday the case was handed over to the federal prosecution service, which deals with major crimes motivated by political and religious extremism.
While police and prosecutors publicly released few details, German media citing unnamed investigators reported that the suspect was known to have extensive links with far-right extremism.
News site Zeit Online said Stephan E. had been previously sentenced to jail for a 1993 failed pipe-bomb attack on an asylum seekers' home in Hesse.
Der Spiegel weekly reported he received a seven-month suspended jail term a decade ago after he had joined hundreds of right-wing radicals in an attack on a May 1 Labour Day march in Dortmund.
He had also repeatedly come to police attention for other acts of violence, weapons and property offences, the magazine reported, adding that he was also believed to have had connections with the neo-Nazi NPD party.
News channel NTV meanwhile linked the suspect to the fascist militant group Combat 18, the number of which stands for the first and eight letters of the alphabet, the initials of Adolf Hitler.
- Racist hate -
If the shooting death was indeed motivated by right-wing extremism, it is believed it would be postwar Germany's first murder of a politician committed by a far-right perpetrator.
Three opposition parties -- the Greens, Free Democrats and far-left Die Linke -- urged a special parliamentary hearing into the case.
In past attacks, several German politicians have been badly injured, among them parliamentary speaker Wolfgang Schaeuble who has used a wheelchair since surviving a 1990 shooting by a deranged assailant.
Cologne city mayor Henriette Reker survived a 2015 knife assault by a man angered by her pro-refugee stance.
From the 1970s to early 1990s, Germany was terrorised by the far-left Red Army Faction, which emerged out of the anti-Vietnam war movement, with shootings, bombings and kidnappings targeting politicians, police, bankers, business leaders and US troops.
More recently Germany was shocked to learn that the far-right militant group National Socialist Underground (NSU) killed nine Turkish and Greek-born immigrants and a German policewoman from 2000 to 2007, and carried out bomb attacks and bank robberies.
Free Democrats lawmaker Benjamin Strasser was among politicians sounding the alarm on Monday, telling media group RND that "for years, threats from the extreme right against politicians have been on the rise".
"We need to decisively clear up and take effective measures against right-wing terrorist structures."