Three men suspected of murdering Hrant Dink were arrested in Istanbul, the city's governor said on Friday.

Dink, the most prominent voice of Turkey's shrinking Armenian community who stood trial for speaking out against the mass killings of Armenians by Turks, was shot and killed in broad daylight at the entrance to his newspaper's offices. Dink, 52, was one of dozens of journalists, writers and academics who have gone on trial for expressing their opinions, most under the infamous article 301 of the penal code, which makes it a crime to insult Turkey, its government or the national character.

Prime Minister Recep Tayyip Erdogan twice addressed  the country to condemn the killing and vow to capture those responsible. The governor called the murder an "assault on the freedom of speech."

In the evening, thousands marched down the street where he was killed, blocking traffic, carrying posters of Dink and shouting slogans in favor of free expression.

Most Turks assumed the shooting was politically motivated, a reaction to Dink's public statements that the mass killings of Armenians around the time of World War I constituted genocide. Nationalists see such statements as insults to the honor of Turks and as threats to national unity.