Japan's finance minister has refused to step down or apologise over remarks suggesting the country can take lessons on changing its constitution from Nazi Germany.

Taro Aso, who also serves as deputy prime minster to Shinzo Abe, said that retracting the comment that outraged neighbouring countries and rights groups was an adequate response and he is not to go further.

"I have no intention of stepping down," Aso told a news conference. "I said I will retract the point that caused misunderstanding, and I think my real intentions have been fully understood."

Opposition party leaders had called for Aso to resign after his seemingly sympathetic comments about Adolf Hitler's handling of internal politics were published by Japanese newspaper the Asahi Shimbun.

Aso, who is known for intemperate remarks, was quoted as telling an ultra-conservative audience in Tokyo: "One day, [Germans] found that the Weimar Constitution was changed to the Nazi Constitution. It was changed without being noticed by anyone. Why don't we learn from that technique?"

The remark triggered outrage in neighbouring countries that suffered Japanese occupation during the Second World War - when Tokyo and Nazi Germany were allies.

Chinese Foreign Ministry spokesman Hong Lei said the comments showed that "Japan's neighbors in Asia, and the international community, have to heighten their vigilance over the direction of Japan's development."

"[Aso's remark] will obviously hurt many people," added South Korean Foreign Ministry spokesman Cho Tai-young.

Also US-based Jewish human rights group the Simon Wiesenthal Center urged demanded an apology from Aso, but he refused.

Japan is discussing changes to its post-war constitution, which was redrafted under heavy American pressure and compels the country to peace.

Aso claimed his remarks have been misinterpreted, saying he was referring to the Nazis "as a bad example of a constitutional revision that was made without national understanding or discussion... I just don't want (the revision) to be decided amid a ruckus."

"His honest feeling is that he simply made a slip of the tongue," one of his aides told the Asahi Shimbun.

In his past political career, the conservative politician drew criticism for saying the ideal country would be one that attracts "the richest Jewish people", telling youths they should not marry if they're poor and for accusing the elderly of being a burden on society.

"We have to think about ways to let them die without delay," he said referring to people in terminal care, before later apologising.