Chinese professor working with Japan's Asia University goes missing after visiting home country

The professor was identified as 61-year-old Fan Yuntao.

He was contacted by Chinese authorities before he disappeared, sources told Kyodo.

Japanese authorities fear he might have been detained.

The whereabouts of Hu Shiyun, a professor at Japan's Kobe Gakuin University, also became unknown in China, the college said in March as quoted by Kyodo.

Their disappearances have drawn attention as China has been strengthening its efforts to safeguard national security, leading to detentions of people, including foreign nationals, on suspicion of engaging in spying activities, Kyodo news agency reported.