Beijing and Tokyo appear to have waited until two of China's key diplomatic and domestic events — the 70th anniversary of Japan's defeat in World War II and President Xi Jinping's visit to the United States — were over before revealing the detention of two Japanese nationals in China for alleged espionage, a Japanese expert on China said Thursday.

On Wednesday, China and Japan announced that two Japanese men were being held on charges of espionage by authorities in Zhejiang and Liaoning provinces, respectively, since May.

"Since there was a possibility that Prime Minister (Shinzo) Abe would attend a ceremony for the 70th anniversary, both sides probably wanted to withhold the information until it was over so that it wouldn't stir up public sentiment," said Satoshi Tomisaka, professor at Takushoku University's Institute of World Studies.