Roh Tae-ak, chairman of the National Election Commission (NEC), speaks during a parliamentary interpellation session at the National Assembly in Seoul, Friday. Yonhap

Roh Tae-ak, chairman of the National Election Commission (NEC), expressed shock, Friday, over President Yoon Suk Yeol's claim that the April 10 parliamentary elections were rigged. He called the deployment of troops to NEC facilities during the brief period of martial law as "unconstitutional."

"I found the president's stance on election fraud shocking," Roh said during a parliamentary interpellation session.

He added that "election fraud is impossible under our system," in response to a lawmaker's question whether Yoon's views seemed to be influenced by conspiracy theories raised by far-right political groups.

The election watchdog chief also stated there was "absolutely no doubt" that the military's unauthorized occupation of NEC facilities and attempts to seize servers during martial law were unconstitutional and unlawful.

During the emergency military rule that Yoon declared on Dec. 3, which lasted for only six hours, nearly 300 soldiers were deployed to three NEC facilites, including its headquarters in Gwacheon, Gyeonggi Province.

Roh's remarks followed Yoon's explanation on Thursday that concerns over election fraud were a key factor in his surprise martial law declaration.

In a public address, Yoon said the NEC's computer systems were vulnerable to cyberintrusion and manipulation, yet the agency had not cooperated with necessary inspections.

"How can our people trust election results when the computer system that manages the elections —the very foundation of democracy — is in such disarray?" Yoon said.

Yoon added that he had demanded improvements before the April 10 general elections, but could not confirm whether those changes were made.

"For this reason, I ordered the minister of national defense to inspect the National Election Commission's computer systems," the president said.

The NEC has since called for a criminal investigation into those involved in the intrusions during martial law, while confirming no internal documents were leaked.