SEOUL — South Korea said Tuesday that North Korea cannot unilaterally nullify the 1953 Korean War cease-fire, calling the North’s war threats a psychological ploy to strengthen Kim Jong Un’s leadership at home and force Washington and South Korea to make concessions to the isolated country.
Following through on a standing threat that it revived last week amid tensions over joint US-South Korean military drills coupled with UN sanctions, North Korea declared that the armistice nullified as of Monday and that the guns of the 1950-53 Korean War, silenced for 60 years under an uneasy truce, could roar again.
North Korea also severed military and Red Cross hot lines and issued a torrent of threats, including a possible ‘‘preemptive nuclear strike’’ against the United States and South Korea.
In North Korea, the authorities were kicking up a war fever — a tool of populace control they had previously used at times of international tension — by having people evacuate into tunnels with emergency provisions and putting up military camouflages on buses and trucks, the South Korean Defense Ministry said Tuesday.
Kim, the North Korean leader, visited front-line artillery units twice in the last week, warning that ‘‘war can break out right now’’ and calling for merciless strikes at the South Korean marine bases he watched across the border through binoculars, according to North Korean media.
Last Friday, Hyon Yong-chol, the chief of the General Staff of the North Korean People’s Army, visited the truce village of Panmunjom on the border, raising fears among some South Koreans that the North might repeat what it had done there in 1996 and send hundreds of armed troops to punctuate its claim that the armistice was no longer valid.
Stressing their alliance against North Korean threats, the office of the South Korean president, Park Geun-hye, said Tuesday that she planned to meet President Obama in Washington in early May. The announcement came a day after the allies began their annual Key Resolve joint military exercises, which are in addition to their two-month-long Foal Eagle drill that began on March 1.
‘‘A unilateral nullification or termination of the armistice is not allowed under its related articles and principles of international laws,’’ said Cho Tae-young, spokesman of the South Korean Foreign Ministry. ‘‘We demand that North Korea withdraw comments that threaten the stability and peace of the Korean Peninsula and the region.’’
Martin Nesirky, a spokesman for the United Nations, which sent allied troops to fight for South Korea during the war, also told reporters that North Korea could not dissolve the armistice unilaterally.
Kim Min-seok, spokesman of the South Korean Defense Ministry, said Tuesday that there was no sign of imminent nuclear or missile tests by the North or hostilities along the border. He said that the ‘‘rhetorical threats’’ flooding the North’s state-run media were aimed at putting ‘‘psychological pressure’’ on the South.
Jay Carney, a White House spokesman, said the United States was ‘‘certainly concerned by North Korea’s bellicose rhetoric. And the threats that they have been making follow a pattern designed to raise tension and intimidate others.’’