French President Francois Hollande and his German counterpart Joachim Gauck will pay joint tribute Sunday to the soldiers who died after Germany declared war on France exactly 100 years ago.

The two leaders will gather at Hartmannswillerkopf to remember the 30,000 soldiers who lost their lives in the fierce World War I battles around this rocky peak in France's Alsace region near the border between the two countries.

In their speeches, Hollande and Gauck will not only remember the sacrifices made but also celebrate their countries' friendship and the construction of a peaceful Europe after World War II.

Last year the two heads of state walked hand in hand to a monument in the central French village of Oradour-sur-Glane where SS troops massacred 642 people on June 10, 1944 during World War II, the worst Nazi atrocity in occupied France. Gauck was the first German leader ever to visit the village.

In Hartmannswillerkopf, Hollande and Gauck will lay wreaths, hold a minute's silence and meet around one hundred young French and Germans exchange students.

They will also lay the foundation stone for the first museum jointly conceived by historians from both countries, which will tell the story of the fighting on the mountain known as "The Eater of Men".

The events "testify to the strength of the friendship between the two countries which allows them to look together at their common history, including at what has been the most dramatic," Hollande's office said.

The symbolism is all the stronger as August 3, 1914 "opened a period of 30 years of conflicts, bitterness, massacres and barbarity between France and Germany," the Elysee added.

Meanwhile, descendants of the first two French and German casualties of the war gathered in the northeastern French border town of Joncherey on Saturday for a ceremony marking the centenary of their deaths, which occurred on the eve of Germany's declaration of war on France when German troops on a reconnaissance mission fired on French soldiers.

In Liege on Monday, a service to mark 100 years since the German invasion of Belgium will be attended by members of the Belgian and British royal families as well as other heads of state and government, including Hollande and Gauck.

London will also hold events in the coming days to mark the centenary of Britain's declaration of war on Germany.

The four-year conflict that became known as the Great War left some 10 million dead and 20 million injured on the battlefields. Millions more perished under occupation through disease, hunger or deportation.