Armenians on Friday marked the anniversary of the deaths of 1.5 million of their ancestors at the hands of the Ottoman Turks exactly 100 years ago, a genocide most of the world has recognized but Turkey continues to deny. 

The somber day was filled with marches and prayers held by people of Armenian descent in Lebanon, Israel, Russia, Iran and Armenia, CBS News reported.  

In Turkey, the pain and sorrow was perhaps most palpable, as it's where Armenians were gathered in 1915 to be slaughtered or deported by the Ottoman Empire during World War I. The empire was at war with Russia and feared Christian Armenians would become its ally.

To this day Turkey remains steadfast in its claim that the deaths of 1.5 million Armenians was not genocide. But their descendants have vowed to not be silenced.

"As Armenians we have come to Istanbul in record numbers to memorialize the brutal massacre of our family members, and to remind the Turkish government that 100 years later we are still seeking justice and accountability," Sarah Leah Whitson, executive director of Human Rights Watch's branch in the Middle East and North Africa, told The New York Times.

Scores of descendants gathered in front of an Istanbul train station holding red flowers and signs reading "genocide, recognize, genocide apologize," according to the newspaper.

Turkey has maintained the deaths were the unfortunate result of civil unrest, and that the actual number is less than 1.5 million, CBS News reported. At one time it was even illegal to refer to the massacre as "genocide."

But a small shift was detected Friday when Turkish President Recep Tayyip Erdogan acknowledged the day of mourning.

"We are cognizant of the sorrowful events experienced in the past by the Armenian community and I sincerely share your pain," Erdogan said, The NY Times reported. The president's comment was a reiteration of a statement given during the last anniversary in April 2014.

Yet there was no mention of the word genocide. Most Turkish newspaper headlines focused on Friday ceremonies commemorating the Battle of Gallipoli, when Turkish forces defeated an invasion of Allied troops.

"We think and we understand that denying the genocide is the continuation of the genocide," Inon Zalcman, a member of the Combat Genocide Association, told CBS News from a commemoration ceremony in Israel.

"More than that, denial of genocide, one genocide, is the opening gate for another genocide."