A former Turkish police informant accused of instigating the 2007 murder of ethnic Armenian journalist Hrant Dink claimed in court Tuesday that he had warned police of the plot but they failed to act. Erhan Tuncel is being retried in an Istanbul court over the high-profile murder after initially being acquitted of all charges in 2012. Tuncel testified on Tuesday that he had informed the former head of police intelligence, Ramazan Akyurek, of the plan to kill Dink but that his warnings went unheeded, according to Turkish press reports. "I have no connection to the murder. I warned them. The murder could have been prevented," he said. Dink, 52, was gunned down in broad daylight by a teenage ultranationalist outside the offices of his bilingual weekly newspaper Agos in Istanbul in a killing that shocked the country. Dink, then Turkey's most prominent ethnic Armenian journalist, had incurred the wrath of Turkish nationalists for calling the World War I massacre of Armenians a genocide. A crowd of demonstrators gathered outside the courthouse for Tuesday's hearing, chanting "the murderer state will be held accountable". Tuncel's allegations appear to back up widespread accusations of a state conspiracy after media reports that security forces had known of the murder plot but failed to act. An Istanbul court in 2011 sentenced Dink's self-confessed killer Ogun Samast, who was tried separately as he was juvenile at the time, to 23 years in jail. A year later, the court sentenced the alleged mastermind of the murder, Yasin Hayal, to life imprisonment but acquitted 18 other defendants including Tuncel, ruling that there was no conspiracy. However an appeals court in May this year ordered a retrial after ruling that there was a criminal conspiracy to murder Dink.