World leaders have paid tribute to former German chancellor Helmut Kohl, the father of German reunification and a founder of modern-day Europe.

Kohl, who died June 16 at the age of 87, was the first person to be honoured with an official memorial event by the European Union in the French city of Strasbourg.

European Union Commission President Jean-Claude Juncker described Kohl as a "European patriot" at the ceremony on Saturday, adding he was a "giant of the post-war period."

"Helmut Kohl was not just the architect of German unity. He contributed substantially, more than others, to the reconciliation between European history and European geography."

During his 16-year term as Germany's leader, stretching from 1982 to 1998, Kohl spearheaded his country's reunification and the creation of Europe's common currency, the euro.

"Helmut Kohl gave us the chance to be involved in something bigger than ourselves," former US President Bill Clinton said, citing Kohl's willingness to put international cooperation before national interests at key moments in history.

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Kohl was widely regarded as having skillfully overcome the fears of Germany's neighbours when an end to the country's decades-long division into a communist east and a democratic west first became a realistic possibility in the late-1990s.

Drawing on his friendships with several world leaders, often forged over hearty meals, Kohl assured the Allied nations that had beaten Nazi Germany in World War II that his country no longer aspired to dominate others.

His successor, German Chancellor Angela Merkel, said Kohl's vision and persistence had paid a historic dividend.

"Without Helmut Kohl, the lives of millions of people who lived behind the (Berlin) Wall until 1990 would have taken a completely different course, including mine," said Merkel, who grew up in communist East Germany. "Thank you for the opportunities you gave me."

French President Emmanuel Macron noted that it was his predecessor, Francois Mitterrand, and Kohl, two men who had experienced the suffering of war on opposing sides, who were able to "overcome the terrible memories of their generation".

Several speakers recalled the poignant gesture of reconciliation in 1984, when Mitterrand and Kohl held hands during a ceremony at a World War I cemetery in Verdun, France.

The ceremony in Strasbourg, which was attended by over 800 dignitaries, concluded with the German national anthem and excerpts from Beethoven's 9th Symphony "Ode to Joy", used as the anthem of the European Union.

Kohl's coffin was draped with the flag of the European Union and then taken to the German city of Speyer for a requiem mass and military honours.

He will be buried in a private ceremony at a cemetery in the city.