'Mongrels Tamed By Yankees': North Korea Issues Threats, Blows Up Roads Leading To South Korea

North Korea blew up abandoned roads and rail lines leading to South Korea on Tuesday, one day after calling the South "mongrels tamed by Yankees."

South Korea fired warning shots near the border in response to the blasts and condemned the North's move as "highly abnormal," Reuters reported.

"It is deplorable that North Korea is repeatedly conducting such regressive behavior," spokesperson Koo Byoung-sam of South Korea's Unification Ministry told reporters.

Video released by the South showed an explosion and a large plume of smoke over a section of road where the North had put up a black barrier, Reuters said.

The North's actions came after it accused South Korea on Friday of using drones to scatter a "huge number" of leaflets over Pyongyang and said the incident could lead to armed conflict.

South Korea's military has declined to say who operated the drones, according to Reuters.

On Monday, North Korean dictator Kim Jong Un's sister, Kim Yo Jong, said the South's military was "chiefly to blame" and accused the U.S. of ultimate responsibility.

"If the sovereignty of a nuclear weapons state was violated by mongrels tamed by Yankees, the master of those dogs should be held accountable for this," she said in a statement released by state media.

The North's military previously said it would "permanently shut off and block" its border with South Korea and had alerted the U.S. to its plans.

North and South Korea are technically at war because the Korean War of 1950-53 ended in an armistice, not a peace treaty.