Afghan friend of Munich shopping centre gunman arrested over suspected role in helping organise twisted massacre plot

AN Afghan friend of the murder-obsessed Munich mass killer Ali David Sonboly has been arrested on suspicion of helping organise the deadly attack.

Police say the 16-year-old may have had a role in setting up a Facebook post to lure people to the Olympia shopping centre -- scene of Friday's horror shooting.

"There is a suspicion that the 16-year-old is a possible tacit accomplice to (Friday's) attack," Munich police said on Sunday evening.

The unnamed suspect is said to have handed himself in to police after the gun rampage, according to German news service DPA.

Baby-faced killer Ali David Sonboly slaughtered nine people in the Munich shopping mall massacre.

Cops believe the horrific attack was being planned for a year.

Flags have been flying at half-mast as mourners gathered to pay their respects on Sunday.

"Bullied schoolboy"; and rampaging killer Sonboly, who had been in treatment for a mental health disorder, bought the pistol he used in the killings on the dark web.

Tearful mourners were pictured clutching each other outside the Olympia shopping mall on Sunday, where grief-stricken Germans have laid flowers in memory of those who were tragically killed.

Seven of the nine victims were teenagers and a further 35 people were injured.

Many of those killed were named yesterday -- with three Kosovans, three Turks, and one Greek person among the dead.

All of them were Munich citizens.

A day after the shopping mall massacre details began to emerge about Ali Sonboly, who received psychiatric help for a mental illness last year, and is believed to have been bullied at school.

The loner son of a taxi driver was obsessed with school shootings and owned a book called "Rampage in Head: Why Students Kill".

Police investigator Robert Heimberger said the 18-year-old shooter had visited the site of the 2009 Winnenden school shooting in Germany and took photos.

Sonboly was said to be obsessed with far-right Norwegian terrorist Anders Breivek, and had the killer as his WhatsApp profile image.

Mr Heimberger said the killer was also an avid player of first-person shooter video games including "Counter-Strike: Source."

Thomas Steinkraus-Koch, spokesman for the Munich prosecutor's office, said there is still no evidence of any political motivation for the crime, or that Sonboly targeted specific victims.

Bavaria's top security official has said Germany needs to be able to call upon its military in times of crisis like Friday night's shooting rampage.

Interior Minister Joachim Herrmann told Welt am Sonntag newspaper Sunday: "In extreme situations like for example the terrorist attacks in Paris and Brussels we should also be able to call upon the Bundeswehr in Germany.

"It makes no sense to say we categorically reject that."