South Korea's defense minister said Tuesday that preliminary findings into last week's landmine explosion inside the Demilitarized Zone (DMZ) point to North Korea and amount to a violation of the armistice agreement.
The Sept. 21 blast injured three South Korean troops inside the DMZ, including one soldier who lost a foot.
"This is a clear violation of the armistice agreement, and since North Korea bears responsibility, we will take corresponding measures," Defense Minister Kang Shin-chul told a parliamentary hearing.
His remarks came a day after the military said North Korean landmines were "highly suspected" of causing the explosions.
South Korea's military and the United Nations Command carried out another joint inspection Tuesday and found a North Korean plastic anti-personnel mine near the blast site.
The Joint Chiefs of Staff said investigators assessed that the unexploded mine was different from the one described by soldiers who were present during the Sept. 21 explosion.
Yang Jin-hyeok of the Joint Chiefs of Staff told lawmakers that the mine was discovered during an on-site investigation earlier Tuesday.
Kang said the military had "a range of necessary measures at our disposal" and would implement them in stages, without providing details.
South Korean President Lee Jae Myung also ordered a swift and thorough investigation into the blast, calling for close cooperation with the U.N. Command.
"The military authorities must transparently reveal the truth behind the case by carrying out a swift and thorough investigation in close cooperation with the U.N. Command," Lee said during a Cabinet meeting.
"In accordance with that truth, we will take necessary measures," he added.
The explosion occurred as troops were clearing a route for a joint South Korean military-U.N. Command inspection of suspected North Korean mine-laying activities south of the Military Demarcation Line.
Two soldiers were seriously injured and another sustained minor injuries.
Lee also warned against spreading what he called "groundless conspiracy theories," saying national security should not become a partisan issue.
The DMZ is officially demilitarized, but its northern and southern boundaries remain among the world's most heavily fortified frontiers and are littered with landmines.
South and North Korea technically remain at war because the Korean War ended with an armistice rather than a peace treaty.
Separately, Lee called for stronger self-reliant defense capabilities based on advanced weapons and ordered accelerated work on nuclear-powered submarines and hypersonic missiles.
He also instructed officials to turn the outcomes of his recent visits to the U.S. and Mexico into concrete national gains while prioritizing housing, employment and financial services for low-income households.