Japan's leader Shinzo Abe drew sharp rebukes from China and South Korea Tuesday after sending an offering to a controversial war shrine, and saying he may not repeat a formal apology for his country's World War II rampage.

Abe, an unabashed nationalist, made a symbolic donation to Yasukuni Shrine, the supposed repository of the country's war dead including 14 infamous war criminals.

The gift of a sakaki tree -- sacred in Shintoism -- appeared to indicate that Abe would not visit Yasukuni during a three-day Spring festival which began Tuesday.

But Beijing and Seoul, which see the shrine as a symbol of Japan's lack of repentance for wartime wrongdoing, were angered by the offering at a time when the focus is increasingly on a statement Abe will make marking the 70th anniversary of the end of World War II.

Observers are waiting to see whether he will make direct reference to his country's "colonial rule and aggression" and express "remorse" and apologise, as previous premiers did on the 50th and 60th anniversaries.

For China and South Korea, which suffered under the yoke of Japan's imperial ambition, Abe's language will be a crucial marker of Tokyo's acceptance of guilt for its march across Asia in the 1930s and 1940s which left millions dead.

South Korean foreign ministry spokesman Noh Kwang-Il said war criminals were "worshipped as God-like figures" at the leafy Tokyo shrine.

"Japanese political leaders should be aware that paying respects and expressing gratitude to such a shrine is an act of denial of the basic premise on which Japan was allowed back into the international community in the wake of WWII," he told reporters in Seoul.

Hong Lei, a spokesman for the China's foreign ministry, cautioned Abe over the symbolic importance of this year's anniversary.

"The Japanese leader must take concrete steps to honour (the country's) commitment of looking squarely at and reflecting upon its history of aggression, properly handle relevant issues, and win the trust of its neighbours and the international community," Hong said.

- 'Strong message' -

Abe suggested in a TV interview broadcast late Monday that provided he says he agrees with previous statements, "I don't think I need to write it again."

Beijing and Seoul argue that Tokyo has not properly atoned for its warmongering and insist that a landmark 1995 statement expressing deep remorse must stand.

But Abe wants Japan to have what he says is a less masochistic view of its history. He has caused waves by quibbling over the definition of "invade" and provoked anger by downplaying Tokyo's formalised system of sex slavery in military brothels.

Japan is regularly lambasted by Beijing and Seoul for a perceived failure to atone for the past, and for being unwilling to face history squarely.

Last week Japanese novelist Haruki Murakami said Japan must continue saying sorry for its aggression until its former victims say "enough".

Omitting a direct apology in the summer statement would damage Japanese diplomacy, Tetsuro Kato, visiting professor at Tokyo's Waseda University, told AFP.

"Japan's relations with neighbouring countries could become worse," he said.

"Denying the history of aggression or simply not mentioning it would be a very strong message" of the wrong kind, he said.

Yasukuni shrine also received offerings from Health, Labour and Welfare Minister Yasuhisa Shiozaki as well as the chiefs of both chambers of parliament.

While the shrine honours more than two million Japanese war dead, it also includes senior military and political figures convicted of prosecuting Japan's aggressive conflict -- and houses a museum that paints Japan as a frustrated liberator of Asia and a victim of WWII.

Abe went to the shrine in December 2013, sparking fury in Asia and earning him a diplomatic rebuke from the United States.

Scores of conservative lawmakers, possibly including cabinet ministers, are expected to go to the shrine on Wednesday to mark the spring festival.

Abe is due to leave later Tuesday for an Asia-Africa summit in Indonesia and will visit the United States later this month. Both occasions are expected to provide clues to the content of his summer statement.