Tens of thousands of people braved blazing heat to pay their respects at a controversial Japanese shrine, as Emperor Naruhito spoke of his deep remorse on the 80th anniversary of the nation's World War II surrender.

Local reports have it that a cabinet minister was among the visitors to Yasukuni Shrine in Tokyo, which honours 2.5 million mostly Japanese soldiers who perished since the late 19th century, but also enshrines convicted war criminals.

Trips to the shrine by government officials seems to have angered countries that suffered Japanese military atrocities, particularly China and South Korea.

The visit came as Emperor Naruhito said he felt a deep and renewed sense of sorrow in a sombre speech alongside Empress Masako in an indoor arena in the centre of the city, where the national flag flew half-mast outside.

Meanwhile, Prime Minister Shigeru Ishiba also addressed the ceremony, pledging to uphold the painful memories of war, by passing the ideology down across generations, and pursue actions toward lasting peace.

Recall that no Japanese prime minister has visited the shrine since 2013, when a trip by then-premier Shinzo Abe sparked fury in Beijing and Seoul, and a rare diplomatic rebuke from close ally the United States.