North Korea promised to “adopt unpredictable measures of revenge” following an exchange of fire between the two Koreas on Sunday, South Korean media reported on Tuesday.

The warning, which said North Korea would continue patrols similar to the one which provoked Sunday’s fire, came despite Washington on Sunday urging Pyongyang to refrain from actions that could risk conflict between the two Koreas.

“We will continue patrol activities near the Military Demarcation Line (MDL) in the future…If [the South] continues its provocations, we will adopt unpredictable measures of revenge,” a message sent by North Korea’s “Northern Representative for High-Level Military Talks”