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Francois Mori, pool, Associated Press
French President Francois Hollande pays respect after he lays a wreath of flowers at the Tomb of the Unknown soldier under the Arc de Triomphe, during the Armistice Day ceremonies marking the end of World War I, in Paris, France, Tuesday, Nov. 11, 2014. The Armistice Day is commemorated every year on Nov. 11 to mark the armistice signed between the allies of World War I and Germany to end the war.

PARIS — Europe marked Armistice Day Tuesday with ceremonies and moments of silence as France opened an international memorial on a former battlefield.

This year's events had special significance because 2014 is the centenary of the start of World War I. Tuesday is the 96th anniversary of the armistice that ended the war on Nov. 11, 1918.

French President Francois Hollande laid a wreath at the tomb of the unknown soldier under Paris' Arc de Triomphe.

Later, he inaugurated an international war memorial at Notre-Dame-de-Lorette, in northern France, in the presence of German, British and Belgian officials. The Ring of Memory carries the names of 600,000 soldiers from over 40 countries who died in the region during the war. Names are listed alphabetically without their nationalities.

"Yesterday's enemies, these men are now re-united in death as if they belong to the same family," said Hollande —whose grand-father was a soldier during the First World War.

Commemorations are made to "pass this memory on to future generations" and "remind the world's leaders of their duties toward peace, security, human rights and democracy," he said.

A few hours before the ceremony, a military helicopter forced a plane dragging a banner calling for Hollande's resignation over the memorial to land.

In Britain, thousands gathered at the Tower of London, where a blood-red sea of ceramic poppies spilled into the moat as part of an art installation paying tribute to soldiers killed in the fighting.

A 13-year-old army cadet, Harry Hayes, planted the final poppy — the last of the 888,246 glass flowers — one for each of the British and Commonwealth soldiers killed in the war. Among the dead was Hayes' great-great-great uncle, Pvt. Patrick Kelly of the 1st Battalion, Irish Guards.

"It is an amazing honor," Hayes told Sky News. "Seeing all these poppies and I managed to plant the last one."

The poppy has been a symbol of remembrance in Britain since World War I, when a poem from the era recalled the fragile flower melding with the dead in Flanders. Queen Elizabeth II observed the two-minute silence privately.

A remembrance ceremony also took place in Belgium in the medieval town of Ypres, where the buglers of the Last Post under the Menin Gate played their haunting tribute to the dead. The gate's vaulted ceiling lists the names of more than 54,000 British and Commonwealth soldiers who lost their lives during World War I and have no known grave.

Along with marching bands, pipers, and members of the armed forces, large crowds of ordinary people marched in what is called the Poppy Parade.

Joan Dabbs from Hereford, England, who served as a nurse in a military hospital during World War II, attended the ceremony in Ypres. "I'm here to pay homage to all soldiers of all wars. My younger brother was killed in Normandy on D-Day. It's a terrible history, but we should never, never forget it," she said.

Virginia Mayo in Ypres, Raf Casert in Brussels and Danica Kirka in London contributed to this story.