© Agence France-PresseFlowers, candles during a ceremony to commemorate the 97th anniversary of the 1915 mass killing of Armenians in the Ottoman Empire on Taksim Square in Istanbul, on April 24, 2012.
Armenians around the world Tuesday marked the 97th anniversary of the World War I massacre of their ancestors by Ottoman Turks, rekindling anger at Turkey for denying the deaths were genocide.

Thousands took part in an annual procession to a hilltop memorial in the Armenian capital Yerevan, carrying candles and flowers to lay at the eternal flame at the centre of the monument commemorating the mass killings in what was then the Ottoman Empire.

"Today we, just as many, many others all over the world, bow to the memory of the innocent victims of the Armenian genocide," President Serzh Sarkisian, who led officials laying wreaths at the monument, said in a statement.

"This day is one of those moments when the entire nation rallies around the unification of our homeland," he said.

Armenians say up to 1.5 million people were killed during World War I as the Ottoman Empire was falling apart, a claim supported by many historians and several other countries.

Turkey angrily denies a genocide occurred and argues up to 500,000 Armenians, and at least as many Turks, died in civil strife when Armenians rose against their Ottoman rulers and sided with invading Russian troops.

US President Barack Obama called for "a full, frank, and just acknowledgment of the facts" of the "brutal" killings.

While denouncing the 1915 massacre as "one of the worst atrocities of the 20th century," Obama did not use the term "genocide," but he implicitly called for Turkey to acknowledge the role of its Ottoman forefathers.

In Yerevan, 75-year-old Tsovinar Tumasian was among those in the procession.

She said her father had fought to save women and children from Turkish attacks and urged other countries to pressure Turkey to accept the killings as genocide.

"If they are not forced to do so, they will not recognise the genocide as fact. They think that with time, everyone will forget about it," Tumasian told AFP as her relatives helped her make her way up the hill towards the monument.

The annual commemoration comes after the dispute between Armenia and its neighbour Turkey was reignited by French President Nicolas Sarkozy's recent attempt to bring in a law criminalising denial of the genocide.

After a diplomatic row erupted, France's top court struck down the law in February on the grounds that it infringed freedom of expression.

Both Sarkozy and his rival presidential candidate Francois Hollande marked the Armenian anniversary in Paris by attending a ceremony and expressing support for the passage of a newly-worded bill that would outlaw genocide denial. France is home to a large Armenian community.

In Lebanon, meanwhile, thousands demonstrated in a suburb of the capital Beirut and denounced Turkey's efforts to expand its influence in the Middle East.

"Can a nation that fills its prisons with human rights advocates and journalists lecture others on the imperative to champion democratic principles and human rights?" asked Patriarch Aram I at a ceremony at the main Armenian church in the suburb of Antelias.

Lebanon has the largest Armenian community in the Arab world, the majority of whom are descendants of those who survived the mass killings.

In Turkey's largest city Istanbul, hundreds of Turkish, Armenian and Kurdish protesters demonstrated in the central Taksim square.

"We are here to say this pain belongs to all of us ... We are trying to share the pain of Armenians," said Senol Karakas, a spokesman for the group.

The Yerevan procession was broadcast throughout the day on all Armenia's national television channels, accompanied by sombre music, documentary footage about the massacres and eyewitness accounts from survivors.

The night before the commemoration, more than 8,000 people led by the youth wing of the nationalist Dashnaktsutyun party held a torch-lit march through central Yerevan, where a group of activists staged their now-traditional burning of a Turkish flag.

"Our action is a protest, a cry of indignation," said one of the marchers, student Hamayak Serobian, demanding that Turks recognise "the brutality of their ancestors".

In Jerusalem, hundreds of Armenians marched to the Turkish consulate.

They carried the red, blue and orange national flag of Armenia, and held up placards bearing black and white photographs of piles of dead bodies, and slogans reading: "Turkey guilty of genocide," and: "Fight to stop the Turkish denial machine."