WARSAW, Sept. 1 (Xinhua) -- Leaders and officials from across Europe and the United States gathered in Gdansk of northern Poland on Tuesday to mark the 70th anniversary of the outbreak of the European war in World War Two.

    Russian Prime Minister Vladimir Putin, German Chancellor Angela Merkel were among the politicians from about 20 European countries and the United States, who participated in the ceremonies in Westerplatte, by the port of Gdansk, on Tuesday.

Soldiers stand guard by the monument of World War Two at Westerplatte, outside of Gdansk September 1, 2009. (Xinhua/Reuters Photo) Photo Gallery>>>

    "Today marks the 70th anniversary of the outbreak of the most terrible of wars. We are in Westerplatte, the symbol of heroic resistance against the stronger enemy," Poland's President Lech Kaczynski said while opening the international part of the ceremonies.

    The shelling of Westerplatte by the German Schleswig-Holstein warship started at 4:45 a.m. on Sept. 1, 1939 and was long considered to have been the first episode in the Nazi aggression on Poland that started the World War in Europe.

    Poland's Prime Minister Donald Tusk said during the Westerplatte ceremonies that the "biggest tragedy in the history of the humankind began in Gdansk on Sept. 1."

(L-R) Poland's Prime Minister Donald Tusk, German Chancellor Angela Merkel and Russia's Prime Minister Vladimir Putin listen to a speech by Poland's President Lech Kaczynski at Westerplatte September 1, 2009, during ceremonies marking the 70th anniversary of Nazi Germany's invasion of Poland. (Xinhua/Reuters Photo) Photo Gallery>>>

    "Why am I speaking about those examples of war cruelties? Because we are all deeply convinced that the memory about those atrocities, about genocide, is perhaps the most important, and the most effective shield against the threat of the next war," Tusk said.

    "I bow my head before WWII victims, it is our duty to accept responsibility for what had happened (then)," said German Chancellor Merkel in her speech delivered during the observances.

    Evil done during the war could not be reversed and "scars will be forever visible," she said. "Here in Westerplatte I recall the fate of the Poles who suffered under criminal German occupation, I recall the Holocaust of European Jews, I recall people who died a terrible death in German death camps, and millions who fell in struggle against the German occupation," Merkel said.

    Poland and Germany have covered a very long road since 1939, she said. "We now have very friendly relations on many planes between our two countries."

    "We have gathered where the first shots of the most bloody war in human history were fired in order to pay tribute to dozens of millions of its victims: soldiers, civilians, people of various nationalities, religions and beliefs," Russian Prime Minister Putin said in his address at Westerplatte.

    The defeat of Nazism was achieved at a great cost. Some 600,000Red Army soldiers fell in struggles in Poland and of the 50 million dead in WWII over half were Soviet citizens, Putin noted.

    Discussing the causes of WWII, the Russian prime minister said it had its roots in flaws of the Treaty of Versailles. Between 1934 and 1939 attempts were made to "calm" the Nazis who took overpower in Germany. This was done through agreements and pacts that were morally unacceptable and politically "dangerous and wrong."

    "The combination of those actions led to the tragic outbreak of WWII and we must admit that such mistakes were indeed made. My country, its parliament condemned the Ribbentrop-Molotov pact. We have the right to expect that other countries will also condemn agreements concluded with the Nazi regime," Putin said.

    Russia not only "admits to mistakes and errors of the past" but also "makes a practical contribution to building a new world based on new principles," Putin claimed.

    Ukrainian Prime Minister Yulia Tymoshenko said in her address that Europe did not need any more divisions, hatred and lawlessness. "Instead, we need compassion, generosity and understanding for suffering."

    During the Nazi occupation in WWII, Poland lost some 6 million citizens and more than half of its national wealth in destroyed factories, burned-down museums, libraries and villages.

    The country was also used as a base for the occupying Nazis' genocide machinery, home to Auschwitz, Majdanek, Sobibor and other death camps built for the annihilation of Jews in Europe.

    After nearly six years, the war in Europe ended on May 8, 1945, with Germany's unconditional surrender.