More than 10,000 people marched silently through Istanbul on Thursday to protest against the acquittals of 17 men tried over the killing of prominent Turkish-Armenian journalist Hrant Dink and commemorate the fifth anniversary of his death.

The crowd stopped and laid red carnations outside the office of the Agos newspaper which Dink edited, and where he was gunned down in broad daylight.

We are all Hrant, we are all Armenians, the crowd chanted. Against fascism, you are my brother Hrant!

Many Turks believe Dink was the target of arch nationalists because of articles he wrote about Armenian identity and references he made to a Turkish genocide of Christian Armenians in 1915 - an accusation Turkey strenuously denies.

A deluge of public criticism greeted the court's decision on Tuesday to acquit the 17 defendants accused of being part of a terrorist group behind the 2007 slaying and to sentence just one man to life imprisonment for helping plan the assassination.

This (verdict) is a scandal. This is why this commemoration turned out to be so strong, said Ufuk Uras, a Kurdish member of Turkey's parliament.

Among those acquitted was alleged ringleader Erhan Tuncel, who was freed after spending five years in jail. Last July, a juvenile court convicted the actual assassin, Ogun Samast, who was 17 at the time of the shooting, to almost 23 years in jail. Samast's father says his son was just a pawn used by others.

Turkish-Armenian novelist and a former Agos editor, Karin Karakasli, addressed the crowd from a window of the newspaper's office.

You can't close the Hrant Dink case, because it's a wound, not just a case ... We promise here that the state will be called to account, she said to rapturous applause.

This verdict has hurt the conscience of millions, Nergis Ozturk, 30, a well-known actress, told Reuters.

Lawyers for the Dink family say they will appeal against the verdict, while many of the country's newspapers urged the judiciary to find the real perpetrators.

Opinion among conspiracy theorists is split over whether Dink's killers were connected to pro-government nationalists or anti-government nationalists seeking to sow mistrust around the ruling AK Party because of its Islamist roots.

Protesters made their suspicions clear, chanting Fascists shoot, AKP protects.

Turkey's President Abdullah Gul and Prime Minister Tayyip Erdogan have said they would refrain from comment until the result of the appeal was known.

The investigation and trial had been seen as a test for democracy and human rights in European Union candidate Turkey.

In 2010, the European Court of Human Rights ordered Turkish authorities to pay 100,000 euros ($128,900)to Dink's family in compensation, saying they had failed to protect Dink even though they knew ultra-nationalists were plotting to kill him.

Seven security officials have already been convicted for failing to relay information on the plot that could have prevented the murder.

(Writing by Simon Cameron-Moore; Editing by Ben Harding)