A man who made bomb threats to the presidential office by phone and social networking is the son of an aide to National Assembly Speaker Chung Ui-hwa, Assembly officials said Monday.

National Assembly spokesman Choi Hyung-du said the suspect was the son of a Grade-4 assistant at Chung’s office.

The aide has offered to resign and left the country soon after he was contacted by police in regard to his son’s alleged threat against the nation’s top office.

The aide’s son, who was not named, was believed to be in his 20s and living in France, the police said. The suspect has reportedly received mental treatment.

Chung’s aide has reportedly tried to persuade his son to return to Korea and cooperate with the police.

The suspect called Cheong Wa Dae’s civil affairs office Sunday around 2:39 a.m. and said he would “bomb the office if it does not show willingness by noon,” he did not elaborate on what he meant by “willingness.”

Police traced the call to France, and beefed up security around the presidential office. A search of the office turned up no explosive devices.

The caller appears to have made similar threats on Twitter two weeks ago, according to Korea’s anti-terrorism officials. The man tweeted warnings to bomb the residence of President Park Geun-hye and her Chief of Staff Kim Ki-choon on Jan. 17.

By Yoon Min-sik (minsikyoon@heraldcorp.com)