The savage rape and murder of a beautiful 19-year-old medical student in Germany at the hands of a teenage Afghan refugee has sparked a frenzied backlash against the 'open door' asylum policy of Chancellor Angela Merkel.

The chairman of the DPoIG police union, Rainer Wendt, said Maria Ladenburger's killing could have been prevented.

He told Bild newspaper: 'We wouldn't have this victim, and so many others, if our country had been better prepared for the dangers that always go along with massive immigration.'

Flower of German youth: The killing of Maria (pictured) has enraged people in Freiburg

Freiburg - the ancient university city where Maria was studying before her brutal death in October - saw a demonstration yesterday by the hard-right anti-immigration Alternative for Germany (AfD) party.

Maria - who died from drowning - was portrayed as 'the victim of Merkel's welcome culture'.

AfD co-chief Jörg Meuthen said: 'We are shocked by this crime and at the same time we see that our warnings about the uncontrolled arrival of hundreds of thousands of young men from Islamic-patriarchal cultures are written off as populist.'

Social media is also burning up with hate messages directed at refugees in the wake of the arrest of a 17-year-old Afghan boy whose DNA has linked him to the murder of Maria, who was the daughter of a high ranking EU legal official.

Maria's body was dumped in the Dreisam river in Freiburg (pictured, left) after she was raped and murdered. Now police are investigating whether the refugee may have also been responsible for the killing of Carolin G (right) last month

The rising tide of public anger makes it increasingly harder for the chancellor - who will seek a fourth term in power in the general election next year - to justify setting no ceiling on the numbers of refugees who may yet arrive.

Currently there are well over one million in the country, several hundred of whom are said by intelligence agencies to be sleepers for the terrorist group Islamic State.

Public anger about the refugee arrivals has been stoked by high-profile crimes involving immigrants, including alleged rapes and other sex attacks at public swimming pools.

The most infamous were mass sexual assaults perpetrated by immigrant mobs on hundreds of women celebrating New Year's Eve outside Cologne railway station.

Ironically Maria worked part-time between her studies helping out migrants in the city but police believe she never met her killer before the night he ambushed her as she rode home from a party on her bicycle, raped her, then drowned her in a river.

The suspect came to Germany in 2015 as an unaccompanied minor.

He is on remand and will stand trial for rape and murder next year after charges are brought at the conclusion of the police investigation.

Angela Merkel (pictured at a conference in Münster last week) recently announced she would seek a fourth term as Chancellor in next year's election

At the spontaneous demo by AfD supporters on Sunday one elderly man yelled: 'We are outraged at the murder of Maria and the fact that it involved an asylum seeker.'

Three hundred counter demonstrators converged on the small group of AfD supporters and police kept the two sides at bay.

But the Internet is harder to police and 3,000 members of the Facebook inititative 'Refugee Help Freiburg' - which Maria was a member of - took down their page on Saturday following numerous threats from neo-Nazis spewing hatred against migrants.

The murder of Maria Ladenburger (pictured) has ignited a fresh round of fury against Mrs Merkel's open door policy

'This is exactly what liberal and open-to-the-world people of Freiburg had feared,' said the local paper in a comment about the online venom now circulating against all refugees.

The BZ daily in Berlin said neo-Nazis were 'rubbing their hands with glee' at Maria's fate, adding: ' This terrible case is a perfect incentive for their propaganda: every refugee is a potential criminal and terrorist! What else? It is a disgusting, characterless reaction.'

Baden-Württemberg's Interior Minister Thomas Strobl (CDU) praised the police and said: 'The alleged offender must now - regardless of his nationality, regardless of the question since when he has lived in Germany - be in court and answer before the law.'

Police are still investigating whether the suspect might also be responsible for the rape and murder of a 27-year-old woman identified as Carolin G near Freiburg last month.