Japan and South Korea are marking 70 years since the end of WW2, when Japan’s surrender to the allies freed Korea from a 35-year occupation.
South Korea’s President Park Geun-hye spoke at a ceremony on Saturday to mark the country’s liberation.
Japan will hold its own ceremony later on Saturday attended by Prime Minister Shinzo Abe and Emperor Akihito, where a minute’s silence will be observed.
On Friday Mr Abe expressed “profound grief” over Japan’s role in the war.
China and South Korea, which both suffered extensively under Japanese wartime occupation, called for a more “sincere” statement from the Japanese premier.
But Mr Abe, a conservative, stopped short of issuing a fresh apology, saying that future Japanese generations should not be “predestined to apologise” for their country’s wartime actions.
Speaking at South Korea’s commemoration ceremony on Saturday, Ms Park said Mr Abe’s remarks “left much to be desired”.
Mr Abe will not visit Japan’s controversial Yasukuni war shrine this year, as he has in previous years, although there will be commemorations at the site.
Koichi Hagiuda, a member or parliament and aide to Mr Abe, visited the shrine with a cash offering on behalf of the prime minister.
“I paid respects to the souls of those who sacrificed their precious lives in the past war,” Mr Hagiuda said
The shrine has been criticised by China and South Korea because along with Japan’s war dead it honours leaders who were later convicted of war crimes.
As well as commemorations that seek to consign wartime atrocities to the past, there will be events that highlight ongoing tensions in the region.
Thousands of South Korean protesters are expected to hold an anti-Japan rally on Saturday. This past week a Korean protester set fire to himself outside the Japanese embassy in Seoul.
And in North Korea, clocks were set back 30 minutes on Saturday to so-called Pyongyang time to remove the country from a shared timezone established under Japanese colonial rule.
In 1995, then-Japanese Prime Minister Tomiichi Murayama issued a landmark apology for Japan’s “colonial rule and aggression”.
His sentiments were repeated 10 years later by then-Prime Minister Junichiro Koizumi.