"Our country inflicted considerable damage and pain on many countries, especially the people in Asian nations," Kan said during a government-sponsored ceremony marking the 66th year of Japan's surrender that effectively ended the war.
This year's commemoration took place as Japan recovers from the devastating earthquake and ongoing nuclear crisis. Relatives of the WWII dead said they also prayed for the catastrophe's victims and families, Kyodo reported.
Kan also vowed to "renew Japan's pledge never again to engage in war and instead to actively contribute to the establishment of ever-lasting peace in the world."
Also attending the ceremony in Tokyo were Emperor Akihito, Empress Michiko, other dignitaries and about 4,900 relatives of the war dead, Kyodo reported.
The commemoration included a moment of silence for the 2.3 million Japanese military personnel and 800,000 Japanese civilians killed in World War II.
"Reflecting on history and sincerely wishing that the tragedy of war will not be repeated," Emperor Akihito said, "I, along with all the Japanese people, pay my heartfelt tribute to those who lost their lives in battles and ravages of war. I pray for world peace and our nation's further prosperity."