The killings, which have been recognized by some countries as genocide, remain a major roadblock in relations between Armenia and Turkey.
A leading Armenian church official, Catholicos Garegin II, led prayers today at a monument in the Armenian capital of Yerevan that memorializes the hundreds of thousands of Armenians who were killed from 1915 to 1918.
Throughout the day, mourners climbed the hill to lay flowers at the memorial where a flame has burned since 1965 -- the 50th anniversary of the start of the mass killings.
Armenian President Robert Kocharian and Prime Minister Serzh Sarkisian were among those paying tribute to the dead.
For many Armenians -- both within the country and from its large diaspora -- visiting Yerevan on April 24 has become an annual ritual.
That's the day, in 1915, that Armenia says Ottoman authorities arrested scores of Armenian academics and members of the intelligentsia amid mass killings and deportations.
More than 20 countries -- including Russia, France, and Canada -- have recognized the killings as genocide.
Armenians say that Turks killed up to 1.5 millions Armenians from 1915 to 1918 as the Ottoman Empire was crumbling.
Ankara maintains that the killings were part of the wider conflict of World War I, and that the number of Armenians who died was closer to 300,000.
Yerevan Wants Recognition Of Genoicide
It is recognition that the Armenians want -- international recognition for what they say was an orchestrated policy of extermination.
Former Armenian Foreign Minister Raffi Hovannisian spoke to RFE/RL about the dispute today at the Yerevan monument.
"I think we don't have to focus on and be excited by the wave of recognition, because the Armenian genocide and the loss of homeland by our people are historical facts," Hovannisian said.
More than 20 countries, including Russia, France, and Canada, have passed legislation recognizing the killings as genocide.
The genocide debate continues to negatively impact ties between Armenian and Turkey.
Turkey and Armenia do not have formal diplomatic relations and the 268-kilometer border between the two countries has been closed since 1993.
Speaking to RFE/RL today, Hrant Margarian, the leader of the nationalist Armenian Revolutionary Federation-Dashnaktsutiun party, said relations could be improved if Turkey would recognize the killings as genocide:
"No state can live while denying its past," Margarian told RFE/RL. "It can't live [while] denying reality. It is good for Turkey to recognize the Armenian genocide."
Ankara, however, doesn't agree. Turkey has said that to establish diplomatic relations it would require Armenia to drop its policy of seeking international recognition for the killings as genocide.
Many countries are wary of doing so, fearing it would damage their own relations with Turkey.
In the United States, the Congress -- dominated by the opposition Democrats -- has endorsed a bill to officially recognize the Armenian killings as genocide.
But despite lobbying from the United States's powerful Armenian lobby, the bill has met with opposition from supporters of the presidential administration, which is eager to maintain good ties with its NATO ally Turkey.
(RFE/RL's Armenian Service contributed to this report.)
'Every Armenian Knows What Happened To Their Ancestors'
By Harry Tamrazian, director, RFE/RL's Armenian Service
"To be Armenian and not know what happened in 1915 is unimaginable. Every Armenian, wherever they are in the world, knows what happened to their ancestors at the beginning of the 20th century. And every Armenian knows that almost the entire Armenian population in Turkey was lost because of an extremist, ethnocentric policy carried out by the government of the Ottoman Empire in 1915.
The issue will not go away. Armenians will not give up or compromise on their tragedy, which they firmly believe was a genocide." more
Do The Killings Constitute Genocide?
By Abbas Djavadi, director, RFE/RL's Azerbaijani Service
"Few in Turkey would deny that Armenians were killed in 1915 during the course of World War I. Opinions vary, however, on how the deportations and killings of Armenians came about; and whether the killings can be labeled a 'genocide' in a similar vein to the Holocaust.
While only a few extreme nationalists dispute the mass killings of Armenians, some liberals have recognized it as a 'genocide.' Most Turkish intellectuals, political analysts, and historians believe that local Armenians, with the help of Russia, were trying to create an independent Armenian state in eastern Anatolia. " more