BERLIN (AFP) - Mourners in Germany stepped up their calls on Monday for the state to honour a young woman who was killed after defending two teenage girls from a group of aggressors at a fast food restaurant.

A petition on the website Change.org had collected 150,000 signatures by Monday evening calling for Turkish student Tugce Albayrak to be awarded a German Federal Cross of Merit, the highest civilian commendation for service to the nation.

After a series of demonstrations and vigils this weekend across the country in Miss Albayrak's honour, a tribute page on Facebook had gathered almost 170,000 "likes".

Her death even drew the condolences of President Joachim Gauck, who told the woman's family that Miss Albayrak "will always be an example" and she had "won our gratitude and our respect".

Though the young woman died on Friday - her 23rd birthday - Miss Albayrak had been in hospital since a violent confrontation overnight on Nov 14 in a McDonald's restaurant carpark near Frankfurt.

She was in the restaurant in Offenbach sitting at a table with friends when she heard screaming coming from the toilets and went to help.

Miss Albayrak found two intoxicated teens being harassed by a group of people and intervened, which prompted the assailants to turn on her, the investigation has revealed.

A few minutes later, while in the carpark, a man violently struck her on the head and knocked her to the ground. The injury left her in a coma from which she never emerged.

Using video surveillance footage police identified and arrested an 18-year-old man in connection with attack. German newspaper Bild reported that the suspect confessed to hitting Miss Albayrak but claimed it was "just a slap".

Bild also published images on its website on Monday that it said showed the assault in the carpark as a dozen people stood nearby. Police, however, refused to authenticate the footage.

Preliminary autopsy results concluded that Miss Albayrak's death was linked to a "blunt shock" to the head, but investigators haven't said whether it was due to the attacker hitting her or the subsequent fall.