China's then-Vice Minister of Public Security Meng Hongwei delivers a campaign speech at the 85th session of the general assembly of the International Criminal Police Organization (Interpol), in Bali in 2016. File picture: Du Yu/Xinhua via AP

London - The wife of the former head of Interpol Meng Hongwei, who has been missing for over three weeks, has said that she's not sure her husband is alive after he was detained by Chinese authorities.

In an interview with the BBC, Grace Meng said that she hasn't heard from her husband since his disappearance and that she's been receiving threatening phone calls.

She had previously said that her husband sent her a social media message telling her to "Wait for my call" on September 25, the day he set off for China from Lyon.

Minutes later, he sent his last message to her, an emoji of a knife, which she said she believed meant he was in danger.

"I think it's political persecution. I am not sure he is alive," she told the British broadcaster in the interview published late Thursday.

She added that she thinks there is "no limit" to what China can do. "They are cruel," she said.

Meng, who resigned from the international police organization at the beginning of October after his wife reported him missing, is under investigation by China's anti-corruption watchdog.

"There is no privilege and no exception in front of the law," China's Public Security Ministry said in a statement earlier this month. "Anyone who violates the law must be severely punished."