Amid Japan's complaints over his China visit, UN Secretary-General Ban Ki-moon warned that it is difficult to move in the right direction if the lessons of history are not understood correctly.

The UN chief, who attended Thursday V-Day commemorations, including a parade and a grand reception gathering dozens of foreign leaders, made the comments in a Friday interview with Chinese media in Beijing.

Yet Senior Japanese officials, including chief cabinet secretary Yoshihide Suga, urged Ban to stay "neutral" and not to visit China at this time as it would indicate, they said, looking to the past rather than the future.

Ban said that "I made it quite clear publicly that it is important to learn from the past".

"If you do not learn correctly from the past, it would be difficult to move ahead toward the right direction. So learning from the past and also looking for a better future - that is the main purpose of my visit to China this time," he said.

Ban observed that there are "some misconceptions that the UN Secretary-General or UN organizations are neutral". Rather than neutral, the UN is "an impartial body", Ban said.

"When you see something which is terribly wrong, I have to criticize, I have to make it correct. In that regard...I can be impartial in discharging my duty as the secretary-general. That's what I believe my job requires," he said.

"And sometimes I have to raise my voice. I criticize the violation of human rights and atrocities. And I have been in very hard talks, sometimes very critical talks, with certain member states," he added.

He said the UN is an impartial, multilateral body, "trying to work on the principles and ideas of the UN Charter".