AFP - A video address from US President Obama provided the icing on the cake to celebrations marking 20 years since the fall of the Berlin Wall sounded the death knell for communism in Europe.

In the surprise message beamed into ceremonies at the Brandenburg Gate, once on the border between East and West Berlin, Obama told cheering crowds: "Even in the face of tyranny. people insisted that the world could change."

Obama's address came after German Chancellor Angela Merkel, who grew up in the communist German Democratic Republic (GDR), on Monday led a throng leaders through the Brandenburg Gate for the climax of a day of emotional celebrations.

More than 100,000 revellers braved wet November weather to see Merkel and leaders including Russian President Dmitry Medvedev give rousing speeches before 1,000 giant dominoes on the former path of the wall were toppled. Related article: Germans remember the night the Wall fell

With former Soviet leader Mikhail Gorbachev and ex-Polish president Lech Walesa also present, the crowd was treated to a live orchestra, a fireworks display and music from Bon Jovi.

The Scorpions hit "Wind of Change", which became the unofficial theme tune of the fall of the Berlin Wall, also rang out through the drizzle.

"Let us never forget November 9, 1989, nor the sacrifices that made it possible," Obama said. "Together, let us keep the light of freedom burning bright for all who live in the darkness of tyranny and believe in the hope of a brighter day."

"It is not only a day of celebration for Germans," Merkel said. "It is a day of celebration for the whole of Europe."

French President Nicolas Sarkozy said the world still needed to live up to the promise of that euphoric night. Related article: Doubts raised about Sarkozy's Berlin Wall memories

"The fall of the Berlin Wall is an appeal, an appeal to all to vanquish oppression, to knock down the walls that throughout the world still divide towns, territories, peoples," he said.

"You dared to dream in the darkness," British Prime Minister Gordon Brown told Berliners. "You proved that there is nothing that cannot be achieved by people inspired by the power of common purpose."

Twenty years ago, following weeks of protests against the regime, the GDR authorities suddenly allowed people to travel to the West, opening the flood gates to a mass exodus.

After 28 years as prisoners in their own country, stunned East Germans streamed to checkpoints and rushed past bewildered guards, many falling tearfully into the arms of West Germans on the other side.

The Berlin Wall was the front line in the Cold War between two nuclear-armed superpowers, the United States and the USSR, a barrier symbolising over 40 years a troubled continent riven in two. Facts about the Berlin Wall

With other regimes in central and eastern Europe also withering, its collapse delivered a fatal blow to communism. Soon even the Soviet Union was a thing of the past, and the Cold War was over.

Twenty years on, Germans look back with emotion.

"It was an immense joy," said Thekla Koehler, who fled West Berlin 25 years ago hidden in a car -- dozens of others died attempting to escape -- and who was cut off from her family until 1989.

But the feelings of joy are tempered by the realisation that despite an estimated 1.3 trillion euros (1.9 trillion dollars) pouring eastwards since unification in 1990, eastern Germany remains poorer than the west.

Merkel admitted as much: "German unity is still incomplete. We must tackle this problem if we want to achieve equal quality of life."