Berlin, Germany: Germany's longest serving post-war leader, Helmut Kohl, the father of German reunification and an architect of European integration, died Friday at the age of 87.

Kohl, a passionate European, helped long-divided Germany navigate the traumatic transition to a reunified country, and later worked with France's Francois Mitterand to put Germany at the core of the European project.

Tributes poured in for the man US former president George H.W. Bush hailed as "one of the greatest" postwar leaders, and European Commission chief Jean-Claude Juncker called the "very essence of Europe".

"We are mourning. #RIP #HelmutKohl," said his conservative party, the Christian Democratic Union (CDU), on Twitter, with a photo of the former leader, who served as chancellor for 16 years.

Kohl died in his house in Ludwigshafen, in the southwestern state of Rhineland-Palatinate, said Bild daily, whose management had close ties with the conservative politician.

Juncker, mourning the loss of Kohl, "a great European and a very close friend", said: "Helmut Kohl filled the European house with life - not only because he built bridges to the west as well as to the east, but also because he never ceased to design even better blueprints for the future of Europe."

Also underlining his contributions, German Foreign Minister Sigmar Gabriel called Kohl "a great statesman, a great German politician, and above all a great European, who did much not only to bring German unity but also for Europe to become one". 

"This is his great legacy. This is what we will remember him for. Our thoughts are with his family and children. A truly great German has died," said Gabriel in a statement.

Chancellor Angela Merkel was due to speak around 1700 GMT in Rome. She learnt of the death of her one-time mentor while en route to Rome, on the eve of a meeting with Pope Francis on Saturday.

- 'Mantle of history' -

Born a Catholic on April 3, 1930 in the western industrial city of Ludwigshafen, Kohl rose quickly through the ranks of the CDU, his ever-smiling blonde wife Hannelore, with whom he had two sons, by his side.

He became chancellor of West Germany in 1982 and oversaw its reunification with the East.

As the Cold War ended with the Berlin Wall coming down in November 1989, he moved to "grab the mantle of history," as he later said, forging a political stature commensurate with his towering height.

Former protegee Angela Merkel lauded Kohl's contribution to German and European integration in 2012, on the 30th anniversary of his becoming chancellor, declaring that Europeans were "united in our luck" thanks to Kohl's efforts. 

Kohl, who served as chancellor for 16 years, considered Konrad Adenauer -- West Germany's visionary first chancellor, who allowed the nation to make a fresh start after World War II -- as an ideological forefather.

Mentor to Merkel, Kohl was later ousted by his protege, who urged their party to drop the self-declared "old warhorse" when he became embroiled in a campaign finance scandal in 1999.

After retiring from politics, he suffered from health problems, and following a serious fall in 2008, was rarely seen in public in recent years.