Japanese media are reporting that two more Japanese citizens are being held in China on suspicion of spying, bringing the total number of such cases to four.

Japan and China last month acknowledged that two Japanese had been arrested in May on suspected spying charges — one in Zhejiang province and the other in Liaoning.

Japan's Foreign Ministry on Monday refused to confirm or deny the reports.

Japan's national broadcaster NHK said over the weekend that the cases involve a woman in her 50s, arrested in Shanghai, and a man in his 60s, arrested in Beijing, both in June.

In 2010, four employees of a Japanese construction company were accused of filming a Chinese military site in Hebei province but were released within weeks.