Tens-of-thousands of Armenians, including top officials, led a series of events to mark the 90th anniversary of mass killings by Ottoman Turks that began in 1915. The small Caucasus Mountain nation says the killings constitute genocide, a claim that Turkey has long disputed.

Armenian President Robert Kocharian led a silent march, and laid flowers at a monument to victims of the killings in the country's capital, Yerevan.

The commemoration follows a candlelight procession Saturday, as Armenians remember those killed beginning in 1915.

Armenia says 1.5 million people were killed or starved to death in what they say was a systematic extermination campaign at a time when Christian Armenians constituted a sizable minority in the Muslim Ottoman Empire.

But Turkey has long maintained that up to 300,000 Armenians and thousands of Turks died in civil strife that accompanied the chaotic collapse of the empire.

The Armenians rose up against their Ottoman rulers and sided with Russian troops when they invaded Turkey as World War I raged throughout Europe.

Bitterness over the issue has long strained relations between the two neighbors, which do not maintain formal diplomatic relations.

Armenian Justice Minister David Arutionian insists that the killings constituted the first genocide of the 20th century, and that Turkey has to admit to this.

In recent weeks, there have been signs of a possible thaw between the two nations.

Turkey has offered to establish a joint commission to study the facts about what happened, while Armenia says it would not demand financial compensation, if Turkey acknowledged the killings as genocidal.

Ankara has come under increasing pressure from the international community, especially as it will soon start talks about joining the European Union.

15 nations including Russia, France and Poland have said the killings were genocide. The United States has not.