China has arrested two Japanese on suspicion of spying, the Chinese Foreign Ministry said on Wednesday.

Japan said that two had been held since May that diplomats were doing all they could to help.

Japan's Asahi newspaper said the two men were from the private sector.

One was taken into custody in northeastern China's Liaoning province near the border with North Korea, and the other in the eastern province of Zhejiang near a military facility, the paper said.

The newspaper added that China appeared to be looking into whether the men were acting under instructions from the Japanese government.

Chinese Foreign Ministry spokesman Hong Lei told a daily news briefing that the two had been arrested "in accordance with the law for engaging in espionage activities. China has already notified Japan of the situation."

Japanese Chief Cabinet Secretary Yoshihide Suga confirmed that two Japanese had been in custody since May. "Diplomats are taking all appropriate steps and providing all possible assistance," he said.

Earlier in the day, Suga said: "Our country is certainly not doing such things. I would like to say that this is the same with regard to all countries."

In 2010, four Japanese nationals were temporarily detained in China on suspicion of entering a military zone and taking photographs without permission.