BERLIN (AFP) - Berlin on Saturday marked the 50th anniversary of the day the Berlin Wall started to go up with a memorial service and a minute of silence in memory of those who died trying to flee to the West. German President Christian Wulff, Chancellor Angela Merkel, who grew up in the East, and Berlin mayor Klaus Wowereit attended a nationally televised commemoration followed by a ecumenical church service at a chapel built where the Wall stood for 28 years. Flags flew at half mast on the Reichstag (parliament) and church bells tolled at noon as Germans were called to observe a minute of silence in remembrance of the 136 people who are known to have died in Berlin between 1961 and 1989 while trying to cross the Wall. Overall figures of those killed while attempting to flee from East to West Germany stand at between 600 and 700. "No one knows the true figure," Wulff told those attending the commemoration in Berlin's Bernauer Strasse, the scene of many escape attempts which today houses a memorial visited by half a million people every year. "We bow our heads in remembrance of all who died at the Wall and of the hundreds who died on the inner German border," he said. "The dead and wounded, the hundreds of thousands who were emprisoned and politically harassed aren't the only victims of this Wall. "Millions were also forced to renounce the lives they wanted to live," he added. "The Wall was part of a dictatorial system, an unjust state," Wowereit said. "It illustrated the bankruptcy of a system people wanted out of. "The Wall is now history, but it must not be forgotten. "It is our responsibility to keep its memory alive and pass it on to future generations ... so that such injustices never repeat themselves," he added. At noon, Berlin's buses and trains stopped for three minutes while local radio stations interrupted their programmes.