Armenia has marked the 91st anniversary of massacres inflicted on Armenians in Turkey under the Ottoman Empire - events Armenians refer to as genocide.
Hundreds of thousands of people marched through Yerevan Monday climbing to a hilltop memorial to lay wreaths in remembrance of the 1.5 million people Armenia says were slaughtered in Turkey between 1915 and 1923.
Armenian-Americans are holding a 91-hour prayer vigil and demonstration outside the Turkish embassy in Washington.
President Bush issued a statement calling it one of the 20th century's most horrible tragedies which he world must never forget.
Turkey strongly disputes the charge of genocide. It says 300,000 Armenians and thousands of Turks died as a result of a Russian-backed Armenian uprising against Ottoman rule.
Ankara has come under increasing international pressure to acknowledge its actions during those years as it seeks membership in the European Union.
Several European countries, including France and Switzerland, recognize the event as genocide.