A general view shows the Four Seasons Hotel building in Hong Kong on February 1, 2017. A Chinese billionaire has been abducted in Hong Kong by mainland agents, according to reports on January 31.

Doubts are rising over missing ­tycoon Xiao Jianhua's grip on his vast business empire, with one source close to Xiao's family ­saying the billionaire's contact with the outside world has been ­severed "in the last couple of days".

The source said that in the days immediately after his return to the mainland from Hong Kong on January 27, Xiao had been allowed limited external contact, including phone calls to his wife.