The son of a former aide to the nations' parliamentary chief was confirmed to have called in threats to bomb the presidential office Cheong Wa Dae over the weekend, a parliamentary spokesman said Monday.

Security around Cheong Wa Dae was tightened on Sunday after a man presumably in his 20s called from a French number to say he was going to bomb the office unless "they showed willingness," police said, adding it was unclear what he meant by "willingness."

Authorities had earlier connected him to the person who tweeted threats to blow up the homes of President Park Geun-hye and her top aide on Jan. 17.

The two men turned out to be the same person, and none other than the son of a former aide to National Assembly Speaker Chung Ui-hwa, Chung's spokesman Choi Hyung-du told Yonhap News Agency by phone.

The former aide used to be the fourth-highest ranked among Chung's entourage and was only identified by his surname Kang.

He had already submitted his letter of resignation on Friday, two days before his son left eight voice messages at the civil affairs office of Cheong Wa Dae to warn of a bombing, Choi said.

He is currently in France to persuade his son to face questioning by South Korean authorities, the spokesman said, adding the son is known to have a history of mental illness without elaborating details.

Kang had worked with Chung since last June and was in charge of arranging external events. He had also worked under Chung briefly when he was the deputy speaker of the National Assembly, according to the spokesman. (Yonhap)