An American flag is placed in the sand of Omaha Beach, western France, on June 6, 2014. Veterans and Normandy residents are paying tribute to the thousands who gave their lives in the D-Day invasion of Nazi-occupied France 70 years ago. Picture: Thibault Camus

Colleville-Sur-Mer, France -

Men who stormed Normandy's shore 70 years ago on Friday paid tribute to comrades killed in the D-Day landings in Nazi-occupied France in a sunrise ceremony that started a day of international commemorations of history's biggest amphibious invasion.

As the sun rose on Friday over a gusty Omaha Beach, flags flew at half-staff. A US military band played Taps, while D-Day veterans from the 29th Infantry Division and serving soldiers stood at attention at exactly 6.30am, the moment on June 6, 1944, when Allied troops first waded ashore.

“Twenty-nine, let's go,” they shouted, then downed shots of Calvados, Normandy apple brandy.

Hundreds of Normandy residents and other onlookers applauded the veterans, then began forming a human chain on the beach.

World leaders and dignitaries including President Barack Obama and Queen Elizabeth II will gather to honour the more than 150 000 American, British, Canadian and other Allied D-Day troops who risked and gave their lives to defeat Adolf Hitler's Third Reich.

They are honouring the mighty battles that helped bring Europe peace and unity - just as bloodshed in Ukraine is posing new challenges and threatening a new East-West divide.

The D-Day invasion was a turning point in World War 2, cracking Hitler's western front as the Soviet troops made advances in the east. D-Day launched the Battle of Normandy and brought the Allies to Paris, which they liberated from Nazi occupation.

Obama declared June 6 a national remembrance day.

In a declaration on Friday, he said: “Seventy years later, we pay tribute to the service members who secured a beachhead on an unforgiving shore - the patriots who, through their courage and sacrifice, changed the course of an entire century. Today, as we carry on the struggle for liberty and universal human rights, let us draw strength from a moment when free nations beat back the forces of oppression and gave new hope to the world.”

Today's conflicts are also on many minds at the D-Day commemorations.

Jeffrey McIllwain, professor at the San Diego State University school of public affairs, will lay a wreath on behalf of educators who have lost students to wars in Iraq and Afghanistan - himself included.

He, like many veterans and world leaders here, is concerned about keeping the memory of D-Day alive as the number of survivors dwindles.

He brought 12 students to Normandy for a course on the lessons of D-Day.

“I make them promise to bring their grandchildren to serve as a bridge to the next generation,” he said. - Sapa-AP