North and South Korean troops exchanged fire along their tense border on Sunday, the South's military said, the first such incident since the rivals took unprecedented steps to lower front-line animosities in late 2018.

Violent confrontations have occasionally occurred along the border, the world's most heavily fortified. While Sunday's incident is a reminder of persistent tensions, it didn't cause any known casualties on either side and is unlikely to escalate, observers said. The Joint Chiefs of Staff in Seoul said in a statement that North Korean troops fired several bullets at a South Korean guard post inside the border zone. South Korea responded with a total of 20 rounds of warning shots on two occasions before issuing a warning broadcast, it said.