President Moon Jae-in stressed his government's unswerving push for a peaceful Korea on Saturday, speaking in public hours after Pyongyang's threat of closing an inter-Korean liaison office.

"Peace is the right of the people to enjoy naturally and establishing the Korean Peninsula of peace, where there's no war again, is the responsibility of the state given by the people," he said during his Memorial Day speech broadcast live.

He added, "In order to protect and establish peace, the government will make all-out efforts for a stronger national defense and more robust security."

The president noted the upcoming 70th anniversary of the outbreak of the 1950-53 Korean War. It began June 25 as the communist North invaded the South.

South Korea's freedom and prosperity today would have been unthinkable without the dedicated services and sacrifice by patriots and veterans, he said.

"A country should repay all sacrifices and devotion," he emphasized. "The government will forever remember those who made the Republic of Korea what it is today and inscribe (their feats) in history."

He pledged continued war remain excavation projects, including those in the Demilitarized Zone.

In the speech, Moon made neither direct mention of chilly inter-Korean relations nor a new overture toward Pyongyang.

The North has been ratcheting up its criticism of the South especially over the spread of anti-Pyongyang leaflets by some defectors and other activists here across the border.

In a statement issued Friday night by the United Front Department, which handles inter-Korea affairs, the North warned that it would "definitely withdraw" from the liaison office in its border city of Kaesong as the first punitive step.

Meanwhile, the 65th Memorial Day ceremony was held at Daejeon National Cemetery in the city located 160 kilometers south of Seoul, with around 300 people in attendance.

The usual venue is Seoul National Cemetery, but the government decided to hold it in Daejeon this year due to reports of a growing number of confirmed COVID-19 cases around the capital. (Yonhap)