President Yoon Suk Yeol speaks during an address to the nation in his office on Thursday. (Presidential office)

The National Election Commission on Thursday blasted President Yoon Suk Yeol’s accusation against the election management system earlier in the day, denouncing his claim as a “self-denial” of the very election system that led him to become president.

In a televised public address, Yoon cited disbelief of the NEC as one of the reasons for declaring martial law last week.

"Allegations of election fraud based on strong suspicion is equivalent to a self-denial of the very election management system upon which he himself was elected president," the NEC said in a statement.

The commission said the repeated claims of election fraud were all proven baseless through judgments of the judicial authority.

"The president's address confirms that the arbitrary occupation of the NEC building and attempt to seize servers without Constitutional or legal grounds were clear violations," the NEC said.

The cited election fraud allegation refers to claims of election rigging made in response to the opposition party’s sweeping win in the April general elections.

In the Thursday address, the president questioned the election authority, citing how it had refused to undergo inspection of its internal system last year after the National Intelligence Service discovered a North Korean hacking attack. Though all government authorities underwent the NIS-led investigations, the NEC cited its immunity from outside investigation under the Constitution, the president said.

Former Defense Minister Kim Yong-hyun, who is said to have advised Yoon on declaring martial law, said in a Dec. 5 interview with SBS that he had sent martial law troops to assess the necessity of an investigation into alleged election fraud.

“Yoon’s claims are exaggerated and not true. Few vulnerabilities were found, but no evidence of outside intrusion into the election system was found. The security system was enhanced prior to the April elections,” NEC said.

“Even if there is a possibility of hacking the election system, it does not lead to election rigging. Election fraud can be staged through organized action from NEC aides, a breakdown of the security management system, and switching out identical amounts of actual voting papers, which is almost impossible,” NEC added.