Japan on Wednesday criticized China's extensive land reclamation in the South China Sea, calling for an end to "unilateral action" apparently aimed at buttressing its claims in disputed waters, Kyodo reported.

"We are gravely concerned about unilateral acts that would seek to change the status quo and raise tensions (in the region)," Chief Cabinet Secretary Yoshihide Suga said at a news conference a day after China said it will soon complete some of its land reclamation on the disputed Spratly Islands.

"Even after completion of the reclamation, it must not be fait accompli," Suga said, indicating Japan will never recognize China's attempts to assert territorial claims in the South China Sea through such activities.