Ceremonies have taken place in Armenia to mark the anniversary of mass killings and forced deportations of up to 1.5 million Armenians.
They commemorate actions by the Ottoman Empire that began on April 24, 1915.
But recognition of the events as genocide has caused friction between EU countries and Turkey, which disputes the figures and the definition.
Turkish President Recep Tayyip Erdogan has challenged the genocide claim and argued anyone making it should inspect the country's Ottoman-era archives because “we have nothing to hide".
In defence of his position, Erdogan said that many of the nations accusing Turkey of genocide have a “bloody past” themselves.
Historians believe events starting on April 24, 1915, was the 20th century's first genocide.
But Turkey disputes the description, says the toll has been inflated and considers those killed victims of a civil war.
For Armenia, the killing of their people in the Ottoman Empire and the surrounding regions during 1915-1923 was masterminded and perpetrated by the government of Young Turks, according to the Armenian account which has been backed by the European Parliament and a number of national governments.
Earlier this month, Turkey condemned separate decisions by France and Italy to officially recognise the mass killings of Armenians as a genocide.
This came after French President Emmanuel Macron signed a decision setting April 24 as a day of annual commemoration — a promise he made in his 2017 presidential campaign.
But Turkey claimed Macron’s promise was geared towards winning the Armenian vote during the elections: “It is inevitable that France's attitude, which is far from amicable, will impact its relations with Turkey in a negative way," said a statement by the Turkish government.
Italy followed suit by approving a motion to officially recognise the killings as genocide. Turkey retaliated that they were using the Armenian claims for domestic political interests.
"It is not surprising that this motion was drafted by the Lega Party, led by Matteo Salvini, who is committed to sabotaging relations between Turkey and Italy," was Turkey's response.