Thousands of Germans paid tribute on Sunday to a 23-year-old student who was murdered after rushing to the aid of two teenage girls who were being harassed by a group of men.

Tuğçe Albayrak died on Friday from injuries sustained two weeks ago when she was attacked in the car park of a McDonald’s in Offenbach, near Frankfurt in western Germany. She received blows to her head, from either a bat or a stone. Blurred footage from CCTV cameras captured the moment when she fell backwards, hitting her head on the ground.

She suffered a traumatic brain injury and later fell into a coma.

Her parents took the decision on Friday, their daughter’s 23rd birthday, to turn off her life support machine, after doctors pronounced her brain dead.

Her alleged attacker, an 18-year-old identified only as Sanel M, from the Sandzak region of south-west Serbia, has admitted attacking Albayrak and is being held in police custody. On the video footage he is shown with an accomplice, who apparently tried to hold him back as he began attacking the student who had earlier intervened after hearing the screams of two women in the McDonald’s toilet who were being harassed. Police are trying to track down the women.

On Sunday hundreds gathered to pay their respects on Oranienplatz in Berlin’s Kreuzberg district, which has a large Turkish community. Albayrak was Turkish by origin. Billed as a “civil courage” vigil, people held up photographs of Albayrak, some with slogans and written tributes.

Outside the Offenbach hospital where she died, and where people had been holding a vigil since the attack on her on November 15, people brought flowers and lit candles and a pianist played the student’s favourite songs as friends released helium-filled balloons with farewell messages attached.

A petition that has so far gathered 100,000 signatures has been sent to Germany’s president, Joachim Gauck, urging him to award Albayrak the national order of merit posthumously.

In a letter written by Gauck to the Albayrak family at the weekend he confirmed he was taking the appeal seriously and expressed his “anger and shock” at the attack.

“Nobody can measure the pain that you, your family and the friends of your daughter must be enduring,” he wrote. He also praised her courage. “Where other people looked the other way, your daughter showed exemplary courage and moral fortitude and stood up for the victims of an act of violence”.

In so doing, he added, she had “become herself a victim of a brutal crime”.

The case of Albayrak has recalled that of Dominik Brunner, a manager from Bavaria who was killed after intervening in a fight five years ago. He was later posthumously awarded the order of merit.