Choi Young-bum, senior presidential secretary for press affairs, speaks during a press briefing at the presidential office on Sunday. Yonhap

The office of President Yoon Suk-yeol immediately struck back at former Foreign Minister and National Security Adviser Chung Eui-yong on Sunday after he defended the previous administration's 2019 repatriation of two North Korean fishermen against their will.

Chung said earlier Sunday the then government of President Moon Jae-in determined the North Koreans' expression of a desire to defect as insincere and decided to deport them, as they had confessed to killing 16 fellow crew members.

Chung also said the North Koreans "were rare, grotesque killers."

"Some claim that we had to accept them into our society as defectors in accordance with our Constitution," he said in a statement. "However, our domestic law stipulates that nonpolitical criminals, like them, should be deported without being allowed into the country. Nonpolitical serious criminals are also not considered refugees under international law."

Just hours later, Choi Young-bum, senior presidential secretary for press affairs, hit back at Chung.

"What officials of the previous administration and the opposition party should do is not to engage in a political offensive, but to cooperate faithfully with the investigation," Choi said.