North Korea fired multiple ballistic missiles hours after South Korea and the United States began joint military exercises, a move Pyongyang called a “dangerous provocation” that risked an accidental clash. South Korea’s military said the missiles were fired from the North’s western region toward the Yellow Sea. It was the first reported test of a ballistic missile since US President Donald Trump took office in January. The allies’ annual Freedom Shield exercises are due to continue until March 20, although live-fire exercises have been suspended after South Korean jets mistakenly dropped bombs on a civilian town near the border last week, injuring 29 people. North Korea has demanded the cancellation of joint US-South Korea exercises, calling them a prelude to an attack. South Korea’s military said the joint exercises were aimed at strengthening the alliance’s preparedness for threats like North Korea. North Korea’s Foreign Ministry said it was a dangerous provocation leading to a serious situation on the Korean Peninsula that could escalate into a physical clash between the two sides with even a single accidental shot, according to state media outlet KCNA. The ministry added that the drills would harm US security. South Korean Air Force Chief of Staff Lee Young-soo apologized on Monday for the “unprecedented” incident in which two jets mistakenly bombed a village. Lee told reporters that it was an accident that should never have happened and should never happen again. The Defense Ministry could not immediately be reached for comment. The area hit by the accidental bombing in Pocheon, about 40 kilometers (25 miles) northeast of Seoul, was outside a military training area near the North Korean border. Residents in the area have long complained about the disruption and dangers caused by the drills.