A German man who has been relentless in his bids to profess his love for Twice singer Nayeon face to face has given a big headache to another of the South Korean girl group's singers - Chaeyoung.

In an angry Instagram post, Chaeyoung, 20, slammed the 25-year-old man, called Josh, for revealing her phone number online.

"We're at our limits to stay quiet and wait for you to stop," she wrote on Sunday (Jan 26).

"Due to the 11 digits that an inconsiderate and disrespectful person posted on the Internet, my phone is bombarded with calls and text messages and I'm going through some needless trouble."

In December, Twice's agency JYP Entertainment had asked the police for help to ensure the girls' safety and privacy.

But an undeterred Josh even boarded the same plane on Jan 1 when Twice were returning to Seoul from Japan, where they had done a special for a broadcaster, reported The Korea Herald.

It is not known how he got hold of Chaeyoung's number but Josh, instead of apologising, tweeted instead that her revelations about the leak had instigated her fans to threaten his friends and their families.

He added that he was hurt by what she had done.

Other Twice followers have expressed outrage that he is now playing the victim game, going online to urge the authorities to deport Josh and ban him from ever returning to South Korea.