China's Foreign Ministry said on Tuesday it would "wait and see" how sincere Japan was after South Korea and Japan reached a landmark agreement to resolve the issue of "comfort women".
"Comfort women" is a euphemism for those who were forced to work in Japan's wartime brothels, an issue that has long plagued ties between South Korea and Japan, as well as between China and Japan.
On Monday, the foreign ministers of Japan and South Korea said in Seoul the issue would be "finally and irreversibly resolved" if all conditions were met.
Chinese Foreign Ministry spokesman Lu Kang said Japan's history of militarism and aggression had brought deep suffering to China and other Asian countries.
"We have always consistently asked Japan to accurately face up to its history of aggression, learn the lessons of history and take concrete actions to win the trust of its Asian neighbours and the international community," Lu told reporters.
Chinese academics estimate about 200,000 Chinese women were forced to work as "comfort women".
Lu said China again urged Japan to face up to its history of aggression and deal with the issue responsibly.
When asked whether China believed Japan was sincere in resolving the issue, Lu said the government would be watching.
"Just like you, as for whether Japan can do it, if its words and actions are consistent from start to finish, we will wait and see."
Chinese ties with Japan have long been troubled by a territorial dispute and what China sees as Japan's failure to properly atone for wartime atrocities, as well as regional rivalry and military suspicion.
But relations have improved since Japanese Prime Minister Shinzo Abe and Chinese President Xi Jinping met in 2014.
A front-page commentary in the overseas edition of the People's Daily, the newspaper of the ruling Communist Party, said the "comfort women" issue formed one part of the history of Japanese aggression.
"The possibility of the Japanese government going back on its word still exists," it said. "The ghosts of the history of aggression could, from time to time, stir up trouble again".
In Taiwan, the self-ruled island China claims as its own and a Japanese colony from 1895-1945, Foreign Minister David Lin said the agreement was "an opportunity for us to have further consultations with Japan on the relevant issues".
In principle, Taiwan wants a clear apology and reparation, he said, but both Taiwan and Japan needed to have more consultations on how to resolve the issue.