The strained relationship between North Korea and the U.S. took another turn for the worse Thursday after South Korea reported that Kim Jong Un’s forces fired at least one “unidentified projectile.” The launch comes less than a week after North Korea test-fired several new weapons systems, the first launches of their kind since Donald Trump and Kim were threatening war with each other in 2017. According to CNN, North Korean state media reported the launches last Saturday were part of a drill to “check the operating ability of large-caliber long-range multiple rocket launchers and tactical guided weapons.” It’s unclear exactly what North Korea fired Thursday, but South Korea said it took place in the North’s western Pyongbuk province, which is believed to be home to one of about 20 of Pyongyang’s undeclared missile facilities.