SEOUL, South Korea — North Korea is preparing to blow up roads crossing its heavily militarized border with South Korea, Seoul said Monday, amid an escalating war of words after the North accused its rival of flying drones over its capital Pyongyang to send.

North Korean troops were working under camouflage on the roads on their side of the border near the west and east coasts, likely preparing to blow up the roads possibly as early as Monday, South Korea’s military spokesman said.

North Korea accused South Korea on Friday of sending drones to distribute a “large number” of anti-North leaflets over Pyongyang, in what it called a political and military provocation that could lead to armed conflict.

Lee Sung-jun, a spokesman for the South’s Joint Chiefs of Staff, declined Monday to answer questions about whether the South Korean military or civilians flew the drones.

In another fiery statement aimed at South Korea and the United States, Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, said on Monday that the South Korean military was “clearly” responsible for the drone intrusion , and that Washington also be held accountable.

“If the sovereignty of a nuclear weapons state is violated by hybrids tamed by Yankees, the master of those dogs must be held responsible,” she said via state news agency KCNA, referring to Seoul and Washington.

The North Korean military said last week it would completely cut off roads and railways linked to South Korea and fortify areas on its side of the border, KCNA reported.

North Korea warned this weekend of a “terrible disaster” if South Korean drones were to fly over Pyongyang again. On Sunday it said it had placed eight fully armed artillery units on the border ready to open fire.

The South Korean military has said its refusal to answer questions about the drones is because to address what the North claims would be to lure Pyongyang into a tactic of making excuses for provocations.

South Korea has been trying to strengthen its anti-drone defenses since 2022, Lee said, when five North Korean drones invaded its airspace and flew for hours over the capital Seoul.

Lee Kyoung-haing, an expert in military drone operations at Jungwon University, said civilians would have no problem obtaining drones with a range of about 300 kilometers, the round trip from the south to Pyongyang, with light loads such as leaflets.

Other experts say that even if citizens sent such drones across the border from the South, it could have been difficult to do so without government permission, or authorities may have failed to track them and to block.

North Korea’s Defense Ministry said Sunday that the drones, which were detected over Pyongyang three days earlier this month, were of the type that required a special launcher or runway and that it was impossible for a civilian group to set them off .

The two Koreas are technically still at war after their 1950-53 war ended in an armistice and not a peace treaty.

The cross-border ties are remnants of periods of rapprochement between the countries, including a summit between leaders in 2018, when they declared there would be no more war and a new era of peace had begun.

North Korea has reintroduced heavy weapons into the demilitarized zone’s border buffer and restored guard posts after the sides declared void a 2018 military agreement aimed at easing tensions.