File photo taken Sept. 27, 2012 shows former German Chancellor Helmut Kohl speaks at an event marking his 30th anniversary of coming to power in Berlin, Germany. [Photo/Xinhua]

Kohl served as German chancellor between 1982 and 1998 and is well known as the "chancellor of unity" for his active political plan bringing west and east Germany together.

Under heavy pressure in 1989 he negotiated with the leaders of the United States and the Soviet Union and secured a peaceful and stable Germany reunification, Deutsche Presse Agentur reported.

He is also hailed for his contribution to European integration and the European single currency and market. He persuaded Germans to give up the then strong Deutsche Mark and adopted euro.

As a leader for Christian Democratic Union (CDU), Kohl was seen as the mentor for Chancellor Angela Merkel.

On late Friday, Merkel paid tribute to Kohl during her visit in Rome saying the news of his death fill her "with great sadness." She said her own life had changed with Kohl's guidance which she was extremely grateful to.

Merkel also called Kohl "stroke of luck of us German," since Kohl seized the historic chance and overcome difficulties to unify Germany.

CDU party posted on Twitter: "We are in sorrow. #RIP #HelmutKohl."

At Kohl's house in Ludwigshafen, flowers were laid by mourners by the staircase.

In 2002, Kohl resigned from lower house of the parliament Bundestag and officially left politics.

He began fighting with illness after a fall and a head injury in 2008, and since then he had to sit on a wheelchair and could barely speak. Kohl received a intestine surgery in 2015 and since then his condition gradually worsened.

He died at the age of 87.