Also commemorating the occasion on Saturday, Emperor Naruhito expressed "deep remorse" over the wartime past, which still haunts East Asia.

"Never to repeat the tragedy of war. We will continue to remain committed to this resolute pledge," said Abe, wearing a face mask at an official ceremony for war dead scaled back because of COVID-19.

Abe, who did not echo Naruhito's reference to remorse, sent a ritual offering to Tokyo's Yasukuni Shrine for war dead but avoided a personal visit that would anger China and South Korea.

South Korean President Moon Jae-in said Seoul was always ready to discuss history disputes with Tokyo.

At least four Japanese cabinet ministers paid their respects in person at Yasukuni, which honours 14 Japanese wartime leaders convicted as war criminals by an Allied tribunal, as well as Japan's war dead.

The shrine is seen by Beijing and Seoul as a symbol of Japan's past military aggression.

Shuichi Takatori, a member of Abe's ruling Liberal Democratic Party, told reporters he made the offering on behalf of Abe as party leader, delivering a message that Abe "paid his respects from the heart to the war dead and prayed for the rest and permanent peace of their souls".

Abe has not gone to Yasukuni in person since a 2013 visit that outraged China and South Korea.

Environment Minister Shinjiro Koizumi, 39, often floated as a future premier, was among the ministers who visited the shrine on the emotive anniversary.

South Korea's foreign ministry spokesman expressed "deep disappointment and concern" over the ministers' visit and said Japan's leaders must show their "deep remorse through action".

Thousands braved scorching heat to pay their respects at Yasukuni, where queues quickly became congested, despite markers and signs seeking to maintain social distance.

Many stood in queues for hours, holding parasols to block the 35-degree heat.

The grandson of Emperor Hirohito in whose name Imperial troops fought the war, Naruhito is Japan's first monarch born after the war. He ascended the throne last year after his father, Akihito, abdicated.

The United States and Japan have become staunch security allies in the decades since the war's end but its legacy still haunts East Asia.

Koreans, who mark the date as National Liberation Day, resent Japan's 1910-1945 colonisation of the peninsula.

China has bitter memories of imperial troops' invasion and occupation of parts of the country from 1931 to 1945.

Japan's ties with South Korea especially are strained by a dispute over compensation for Koreans forced to work in Japan's wartime mines and factories.

Australian Associated Press