North Korea conducted military drills involving a mortar firing competition on Monday, according to state media, after warning the U.S. and South Korea against going through with planned joint military exercises this month.

The Korean Central News Agency (KCNA) reported Tuesday that top military officials Pak Jong Chon and Ri Yong Gil oversaw the drills, without leader Kim Jong Un attending.

The drills saw mortar artillery units go head-to-head in a live-fire training competition, while photos showed small groups of soldiers firing mortar shells at circular targets painted on a hillside.

The event was an “opportunity to demonstrate our