World leaders past and present gathered in the German capital on Monday to celebrate the 20th anniversary of the Berlin Wall's fall, which led to German reunification and hastened the demise of the Soviet Union.

Images of the historic night of Nov. 9, 1989, when East Berliners trapped behind the 3.6 metre (12 feet) high concrete barrier rushed checkpoints to force it open, have dominated German television and newspaper coverage for the past week.

As part of Monday's celebrations, 1,000 giant painted dominoes have been set up along a 1.5 km (0.9 mile) stretch of the Wall's original path next to the Brandenburg Gate.
 They will be toppled on Monday evening in the presence of visiting leaders from Britain, France and Russia, in a symbolic re-enactment of a day that shook the world.

"Its majesty lies not in the presence of a structure, but in its absence," British Prime Minister Gordon Brown said in pre-released excerpts from a speech he will give on Monday evening. "The wall is gone. Two Berlins are one. Two Germanys are one. Two Europes are one."    

US Secretary of State Hillary Clinton is also in Berlin and on Monday she met Chancellor Angela Merkel, the first German leader to have grown up behind the Wall in communist East Germany.

Merkel, who was working as a scientific researcher in East Berlin 20 years ago, has called the fall of the Wall "the happiest day in recent Germany history".   

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

Initially a make-shift fence of barbed wire, it was gradually built up into an imposing barrier that encircled the three western sectors of the city and was patrolled by border 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 escape. Thousands of others managed to evade the minefields, guard dogs and watchtowers, using schemes including tunnels, aerial wires and hidden compartments in cars to make it to the West.

The Wall fell after Politburo member and spokesman Guenter Schabowski told a news conference that East German citizens could leave through border crossings, effective immediately.

He was unaware the decision was not supposed to be announced until 4 am the next morning. Watched by thousands on television, he prompted a rush to the border that unprepared, overwhelmed eastern guards were unable to contain.

With some people, the 1990 reunification of the country remains a sore point. A poll of over 1,000 Germans for the Leipziger Volkszeitung daily showed one in eight wanted the Wall rebuilt -- with the numbers nearly equal in East and West.

Thousands of tourists have poured into Berlin to mark the event. Figures from the era that ushered in the collapse of communism in eastern Europe, including ex-Soviet leader Mikhail Gorbachev and Polish Solidarity union leader Lech Walesa, are also taking part in commemorations.

Gorbachev, ex-chancellor Helmut Kohl and former US President George Bush Senior, who led their respective countries in November 1989, appeared in a double page newspaper advertisement in Germany.

"No wall is ever strong enough to strangle the human spirit," Bush said in a comment alongside a photo of the three. - Reuters