Despite a recent improvement in bilateral ties, Foreign Minister Taro Kono and his Chinese counterpart Wang Yi remain at odds over issues related to the East and South China seas, a government official said Thursday.

During a half-hour talk with Wang in Singapore, Kono voiced concern about China's military buildup in the South China Sea, where Beijing and several Southeast Asian countries have overlapping claims, the Japanese official said.

Kono also conveyed Japan's unease about China's moves in the East China Sea, where China is sailing naval vessels around the disputed Senkaku Islands and developing energy resources in the contested waters.