The Berlin Wall's construction 50 years ago must be a constant reminder to citizens today to stand up for freedom and democracy, the city's mayor said Saturday as a united Germany commemorated the bitter anniversary.

Seeing Berlin divided by the 140-kilometre-long wall tore apart the country as well as separating the city's streets, neighbours and families, Mayor Klaus Wowereit said at a televised ceremony.

"It is our shared responsibility to keep the memory alive and to pass it on to the coming generations as a reminder to stand up for freedom and democracy to ensure that such injustice may never happen again," Wowereit said.


German Chancellor Angela Merkel, centre, and President Christian Wulff, left, speak to spectators as they attend the commemoration of the 50th anniversary of the construction of the Berlin Wall. (Markus Schreiber/Associated Press)

German Chancellor Angela Merkel — who grew up behind the wall in Germany's communist eastern part — also attended the commemoration in Berlin, where parts of the wall and an attached surveillance tower now form a museum.

Germany had been divided into capitalist western and communist eastern sectors after the end of the Second World War. At the height of tensions between the United States and the Soviet Union, the East German regime started building the wall through the capital on Aug. 13, 1961.

For 28 years until its collapse on Nov. 9, 1989, the wall was the epicentre of the Cold War, splitting Berlin in two and dividing a nation with two million tons of concrete, 700,000 tonnes of steel, attack dogs, tank traps, death strips and tripwires.

From the very first day it went up, anyone who tried to escape risked betrayal, prison, or death. Hundreds of east Germans were arrested while trying to flee to democratic Western Germany and at least 136 were killed trying to cross the wall.


Achim von Almrich lights a candle at the Berlin Wall Memorial at Bernauer Strasse in Berlin. (Markus Schreiber/Associated Press)

German President Christian Wulff said the "life-asphyxiating wall" must be a reminder to appreciate and preserve the "openness of today's world."

"When I was seven years old, I still went with my grandmother — just a few days before the construction of the Wall — from East Berlin's Pankow [neighbourhood] to West Berlin, and for me as a child it was totally inconceivable that Berlin was suddenly divided," Merkel has said ahead of Saturday's ceremony.

"From that moment on, I couldn't go to visit my grandmother in Hamburg anymore. I couldn't see my aunt or my cousins anymore. That of course marked my entire life," Merkel said in unusually personal remarks.

Canada proud to oppose 'symbol of tyranny': PM

In a statement Saturday, Prime Minister Stephen Harper said Canada is proud to have stood with those who opposed all that the Berlin Wall came to represent as a "symbol of tyranny," while also welcoming so many people who escaped Communist oppression.

"During the Cold War, many apologists for the Communist regime tried to convince the world that their ideology was superior," Harper said. "Fortunately, talented and courageous artists, writers and ordinary citizens were able to expose that what went on behind the Wall ran counter to all the ideals the West had fought for and the truth began to trickle out."

Harper also said the world continues to see the consequences of the "dire legacy of Communist totalitarianism and blind ideology" in North Korea.  

"Like the East Germany of the past, the North Korea of today continues to forcibly prevent its population from building better lives at home or abroad," the prime minister said.

Today in Berlin, only a few of the wall's roughly 3½-metre-high concrete slabs remain standing — haunting reminders of the city's decades of division.

Part of the nearly 40-kilometre path that the wall wound through the heart of the city is marked today by a cobblestone strip, which stretches down streets and across sidewalks to remind passers-by where the wall once stood.