BERLIN - Chancellor Angela Merkel and other leaders hailed the human courage that toppled the Berlin Wall, saying the historic events of 20 years ago showed the world could tackle new challenges, from poverty to climate change.

Merkel and fellow leaders from Britain, France and Russia spoke to tens of thousands gathered at the Brandenburg Gate to celebrate the anniversary of the collapse of the Wall, which ended the Cold War and paved the way for German reunification.

Together we brought down the Iron Curtain and I am convinced this can give us the strength for the 21st century, said Merkel, who grew up behind the Wall herself in communist East Germany.

Our good fortune obliges us to take on the challenges of our time, she added, mentioning security, economic well-being and protection of the environment as key tasks confronting the world.

The spirit of celebration was dampened somewhat Monday by a steady downpour, which forced spectators gathered around the illuminated Brandenburg Gate to cover themselves with plastic rain coats and umbrellas.

French President Nicolas Sarkozy said the fall of the Wall was a liberation, but also a call to nations to fight against repression, to fight against the walls that still exist in our world and which still divide cities, regions and nations.

His Russian counterpart Dmitry Medvedev said the confrontation of the Cold War was in the past and urged the building of a new, better world and a common battle against economic crisis, crime, terrorism and poverty.

After the leaders spoke, they watched the symbolic toppling of a chain of giant brightly colored dominoes set up along a 1.5 km (0.9 mile) stretch where the Wall once stood and where Berliners from East and West celebrated on November 9, 1989.

DEADLY BARRIER

Backed by the Soviet Union, the East German government began erecting its anti-fascist protection barrier in the early hours of August 13, 1961, to end a mass flight of its citizens into capitalist West Berlin.

Initially a makeshift fence of barbed wire, it was gradually built up into an imposing 156-km (97-mile) barrier that encircled the three western sectors of the city and was patrolled by guards who were ordered to shoot anyone who tried to escape.

According to a study published this year, at least 136 people were killed at the Berlin Wall between 1961 and 1989 while trying to flee.

But not a single shot was fired when the Wall fell and the night turned into a giant city-wide party with easterners roaming the streets of West Berlin in disbelief and residents from both sides of the Wall embracing each other impulsively.

(Writing by Noah Barkin, editing by Mark Trevelyan)

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