Germany's longest-serving foreign minister Hans-Dietrich Genscher, a one-time refugee from the communist East who helped unite his divided homeland, has died at the age of 89.

Genscher died of heart failure at home surrounded by his family on Thursday night, his office said in a statement on Friday. Chancellor Angela Merkel led tributes to him.

"We mourn for a great German and convinced European," a sombre-looking Merkel said in a television address, adding that she bowed with respect before his life achievements.

"Personally, I am thankful for all the talks and meetings at which I could draw on his world experience and worldly wisdom."

Genscher, who fled East Germany in 1952 and joined the liberal Free Democrats (FDP) party, reached the height of his power as reunited Germany's first foreign minister.

FDP leader Christian Lindner said on Twitter that Genscher had made history, calling him "the architect of unity (and) one of the founders of the EU".

Compared by some commentators to U.S. Secretary of State Henry Kissinger and Napoleon's foreign minister Talleyrand, Genscher employed his wily diplomatic skills to win support for reunification among doubting allies and former enemies.

With then Chancellor Helmut Kohl, Genscher persuaded Moscow to give up communist East Germany, its staunchest Cold War ally, and let it join the former “enemy West Germany.

And by stressing the then Bonn government's total commitment to the West and to the European integration he championed, Genscher helped reassure Western allies worried that an assertive new German giant was about to be born.

His persistence was rewarded on Oct. 3, 1990, when West and East Germany reunited after signing a treaty with the four victorious World War Two powers to restore the country's full sovereignty after 45 years.

PRAGUE SPEECH

It was in September 1989, during the tumultuous days leading up to the fall of the Berlin Wall, that Genscher gave his most famous speech, which was left unfinished as it reached its peak.

Thousands of East Germans desperate to leave their country had taken over Bonn's embassy in Prague, hoping to go from there to West Germany, and Genscher had swept in to deal with the political and humanitarian crisis that had developed.

That evening, he stepped out onto a balcony of the embassy and told the crowd in the garden below: "Fellow countrymen, we have come here to tell you that your departure ..."

The refugees burst into wild cheers, drowning out his words, as they knew they could now leave. Weeks later, the Berlin Wall opened as East Germany was on the brink of collapse.

"His speech ... made him a symbol of hope, not only for people in both parts of Germany, but also for people in Eastern Europe and beyond," European Commission President Jean-Claude Juncker said in a statement.

German government spokesman Georg Streiter said Genscher was "a great statesman, a great European and a great German".

Born on March 21, 1927, at Reideburg, near Halle, Genscher served in the Luftwaffe (air force) towards the end of World War Two. He said it was only many years later that he learned his name was entered in the rolls of Nazi Party members.

He suffered his worst political moment in 1972, as interior minister, when a police operation to rescue Israeli athletes kidnapped by Palestinians at the Munich Olympic Games ended with the deaths of 11 members of the Israeli team.

Two years later he became foreign minister, a post he held until 1992. As head of the small FDP, often a junior partner in Bonn coalitions, his decision to switch sides in 1982 ended the chancellorship of Social Democrat Helmut Schmidt and brought Kohl, a Christian Democrat, to power.

A passionate supporter of the European Union, Genscher also helped pave the way for the euro with a memorandum on a European central bank and a unified currency area, one of the early steps that led to the launch of the common currency in 1999.

More controversially, he was instrumental in Germany's quick recognition of an independent Croatia in 1991, a decision considered by many to have been a trigger for the uncontrolled breakup of the former Yugoslavia and the region's subsequent slide into war.