The image of a man who looked to be in his late 20s was taken from a security camera on the street where Dink was killed. Police asked for the public's help in finding the suspect.
Several people were detained for questioning, but Interior Minister Abdulkadir Aksu today said there are no suspects in police custody.
No motive for the attack has been confirmed, but Dink's colleagues and friends say they suspect politics.
Dink had angered Turkish nationalists and was prosecuted by authorities several times for saying the mass killings of Armenians by Turks in the early 20th century amounted to genocide, which Turkey denies.
Thousands of Turks marched in Istanbul late Friday night in support of free speech. Today, mourners gathered at the spot where Dink was killed.
The murder has been condemned by human rights groups, the Armenian government, the EU, and the United States.
(AFP, dpa, AP)