Handout picture released on June 7, 2018 by the Police of Wiesbaden shows Iraqi asylum seeker Ali Bashar, 20, suspected of the rape and murder of 14-year-old Susanna Maria Feldman

The escape of a failed Iraqi asylum seeker suspected of raping and murdering a teenage girl sparked outrage in Germany on Friday, raising questions over immigration and police failings.

Ali Bashar, 20, is believed to have strangled 14-year-old Susanna Maria Feldman after sexually assaulting her.

As police hunted Bashar after discovering Feldman's body near a railway line this week, it emerged that he had fled to Iraq with his family on false identity papers.

Bashar also turned out to have chalked up a long police record over less than three years in Germany and should have been expelled months ago.

"The government should beg for forgiveness from Susanna's parents", said the top-selling daily Bild.

"The only thing that is worse than the murder of a child is the murder of a child by a criminal who should not have been in our country."

The case puts renewed pressure on Chancellor Angela Merkel's government over the decision to open Germany's borders at the height of Europe's refugee crisis in 2015, which led to the arrival of more than a million asylum seekers over two years.

Critics charged that the authorities lost control over who they were letting into the country.

Bashar arrived in Germany in 2015 along with his parents and five siblings.

He should have been deported after his request for asylum was rejected in December 2016, but he obtained a temporary residence permit pending his appeal.

During this time, he got into trouble with the police on several occasions, including for alleged robbery, possession of an illegal switchblade and fights.

He was also among suspects of the rape of an 11-year-old girl living in the same refugee shelter as him.

"The girl was raped by an Ali. There were four Alis living in the refugee home," said Stefan Mueller, West Hesse police chief.

The latest crime is reminiscent of another case involving the rape and murder of a student by an asylum seeker claiming to be from Afghanistan.

Hussein Khavari was in March sentenced to life in jail for the deadly attack on medical student Maria Ladenburger, 19, in October 2016.

Tagesspiegel daily pointed to a third case in which a teenage girl was stabbed to death by her boyfriend, an Afghan asylum seeker.

"What is particularly sad in these three cases is also that the victims "were interested, curious and ... tried to befriend (the newcomers).

"That's how integration usually works -- there are hundreds and thousands of examples in Germany. But now also three dead girls," it added in an editorial called "poison for society."