At least 15 people were injured in South Korea on Thursday after fighter jets accidentally dropped eight bombs on a civilian area during a live-fire joint exercise with U.S. forces, the South Korean Air Force and fire officials said.

The incident involving the Air Force KF-16 aircraft, in the city of Pocheon near North Korea, was part of routine drills held by the South to maintain combat readiness against potential attacks from the North.

The drill was in preparation for Freedom Shield, an annual U.S.-South Korea joint military exercise that is set to kick off on Monday.

Just after 10 a.m. local time (8 p.m. Wednesday ET), eight 500-pound MK-82 bombs were “abnormally released” by two air force KF-16s, landing outside the designated firing range, the South Korean Air Force said. 

The air force said four of the bombs misfired because one of the fighter jet pilots entered incorrect coordinates during the flight preparation process, and that further investigation was needed to determine why the second jet incorrectly dropped the four other bombs.

“There are procedures to verify coordinates both on the ground and in the air. However, it appears that a mistake was made in this process,” South Korea’s Joint Chiefs of Staff (JCS) said.

The JCS said live-fire drills were being suspended but that the Freedom Shield exercise would go ahead as planned.

Two of the 15 people were civilians with serious but not life-threatening injuries, fire authorities told reporters. Those with minor injuries included two soldiers who were at a military chapel and two foreign nationals who were in the area.

Eight buildings also sustained damage, officials said, including the chapel, five houses, one warehouse and one greenhouse.

Photographs from the scene showed debris at the church and residences with shattered windows. Residents were being evacuated as authorities searched for any unexploded bombs.

The fighter jet was participating in a combined live-fire exercise involving both the South Korean Air Force and Army, the air force said.

“We sincerely regret the civilian damage caused by this accidental release and wish for the swift recovery of the injured,” it said. “The Air Force will actively implement all necessary measures, including compensation for damages.”

South Korean officials said earlier Thursday that U.S. and South Korean forces were holding combined live-fire drills in Pocheon in their first such exercise this year.

U.S. Forces Korea confirmed that U.S. service members were participating in the drills but said no U.S. Air Force aircraft was involved.

“The safety of the local community, U.S. and ROK personnel is our top priority. We take this incident very seriously,” Col. Ryan Donald, spokesperson for U.S. Forces Korea, said in a statement, using the initials for South Korea’s formal name, the Republic of Korea.

“We are coordinating closely with the ROK Ministry of Defense and are committed to a thorough and transparent investigation,” he said.

South Korea, a U.S. treaty ally, hosts about 28,000 American service members. The Freedom Shield exercise, which runs from March 10 to 20, is designed to strengthen the alliance’s combined defense posture in the face of growing threats from nuclear-armed North Korea.

Since last year’s exercise, North Korea has deepened its partnership with Russia, including by sending weapons and troops to support its war in Ukraine.

After the accidental bombing on Thursday, the governing People Power Party urged a swift and transparent investigation, immediate support and compensation plans for affected residents and enhanced safety measures for training grounds near civilian areas.

“Given that military training takes place near civilian areas, ensuring the highest level of safety management must be a priority,” chief spokesperson Kim Dae-sik said in a statement, adding that the accident “raises serious concerns about basic safety checks and management protocols.”

Lee Jae-myung, leader of the main opposition Democratic Party, also wished those who were injured a swift recovery and called for a thorough investigation.