French President Francois Hollande and his German counterpart, Joachim Gauck, on Sunday marked the centennial of the start of World War I with a joint ceremony at the observation post on Hartmannswillerkopf, a mountain that was the scene of intense fighting during the war.

The observation post in the Vosges mountains of Alsace, a region in northeastern France, changed hands eight times between December 1914 and 1915.

Some 30,000 soldiers from both countries died in the fighting around the rocky spur in the months after Germany declared war on France on Aug. 3, 1914.

Hollande and Gauck shook hands, embraced and participated in a military ceremony before placing the cornerstone of what will be the first Franco-German museum to tell the story of "The Great War."

The museum is scheduled to open in 2017.

Hollande and Gauck visited the crypt that contains the remains of 12,000 unknown soldiers and made their way to the front line, a walk that allows visitors to learn firsthand about the horrors of war.

Belgium's King Philippe, meanwhile, honored cavalryman Antoine Fonck, the first Belgian soldier to die in World War I, at a ceremony in the eastern town of Thimister-Clermont that was attended by more than 1,000 people.

Fonck died on the Thimister-Clermont battlefield on Aug. 4, 1914, the day that the German occupation of Belgium started.

King Philippe placed a wreath at the monument in Thimister-Clermont to Fonck, who was only 21 when he died fighting to defend neutral Belgium from German troops.

The commemoration of the start of World War I will continue on Monday in Liege, Belgium, where about a dozen heads of state and government, including Spain's King Felipe VI, will participate in a ceremony, Belgian officials said. EFE