|Naoto Kan, Japan's prime minister, said it was 'desirable' for China to free Liu [EPA]
China has denounced the Nobel Peace Prize awarded to dissident Liu Xiaobo as tantamount to "encouraging crime", as state media said the prize was part of a Western "ideological war" against Beijing.
The comments came on Thursday as China faced fresh international pressure, with Norway criticising Chinese retaliatory steps over the award and Naoto Kan, Japan's prime minister, speaking out in favour of releasing Liu.
"Liu Xiaobo is a convicted criminal. Awarding the Nobel Prize to him is equivalent to encouraging crime," Ma Zhaoxu, a foreign ministry spokesman said.
Ma did not directly comment on the Kan's comments, but earlier in the day questioned the motivations behind the support of "foreign politicians and governments" for Liu.
"Could it be that they object to China's path of development, object to China's political system?" Ma said.
The Japanese prime minister spoke out in Liu's defence at a time the two countries are trying to repair ties.
In comments made on Thursday, Kan said it would be "desirable" for China to free Liu but stopped short of making an explicit call for his release.
"Japan-China ties are now returning to the original point of [improving] strategically mutually beneficial ties. In this situation ... my position is to act by taking into consideration national interest as well as my personal views."
Ties between Asia's two biggest economic powers worsened after Japan held a Chinese trawler captain whose boat collided with Japanese patrol ships near disputed islets.
But signs of improvement followed recent informal talks between Kan and his Chinese counterpart, Wen Jiabao.
The award has strained China's ties with Norway, home to the Nobel Peace Prize committee, even though the government there has no say in who receives it. China has cancelled several meetings with Norwegian officials since last week.
Ma said that step was "understandable".
Japan greeted the award by stressing the importance of respecting human rights, but unlike some countries, it has not specifically called for Liu's release.
Japan needs good relations with its biggest trading partner but Kan has already come under fire domestically for appearing to cave in to Beijing's demands by releasing the trawler captain.