Thousands of people have gathered in the Armenian capital, Yerevan, to remember the victims of mass killings of Armenians by the Ottoman Turks and push world governments to officially accept the term “genocide.”

Crowds of people marched with candles and flowers up to a hilltop memorial Tuesday to commemorate the 97th anniversary of the World War One-era deaths, which is observed on April 24.

Armenia says the killings of 1.5 million people between 1915 and 1923 constituted genocide, a charge rejected by Turkey. Turkey strongly denies there was a systematic campaign against Armenians and claims that Turks as well died in civil unrest during the fall of the Ottoman Empire.

U.S. President Barack Obama released a statement honoring the victims and calling for a “full, frank and just acknowledgment of the facts” of the killings. While denouncing the massacres as “one of the worst atrocities of the 20th century,” he stopped short of using the term genocide. But he said “moving forward with the future cannot be done without reckoning with the facts of the past,” an implicit call on Turkey to acknowledge its role.

Mr. Obama described the Armenian deaths as genocide while campaigning for president but has not done so since taking office. In Tuesday's statement, he said his view of those events has not changed.

Mr. Obama's statement said he supports efforts by both Armenians and Turks to foster a dialogue and explore reconciliation.

He referred to the tragedy as the “Meds Yeghern,” a term Armenians use to describe the massacres, and urged the American people to recommit themselves to ensuring that such devastating events are never repeated.

Many countries worldwide have officially recognized the mass killings of Armenians as genocide. But the Turkish government has pressed its allies, including the United States, to refrain from doing so.