SEOUL, South Korea — At least 15 people were injured in South Korea on Thursday after a fighter jet accidentally dropped eight bombs on a civilian area during training linked to joint military drills with the United States, the South Korean Air Force and fire officials said.

The South Korean military said the training in Pocheon, a northeastern city of about 140,000 people near the heavily fortified border with North Korea, 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 an air force KF-16, landing outside the designated firing range, the South Korean Air Force said in a statement. 

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, adding that it was investigating the cause of the accident and the extent of the damage.

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

Pocheon Mayor Baek Young-hyun called for all military training to be completely suspended, describing what happened as a “horrific accident.”

“The government must recognize the severity of this accident and respond with swift and decisive action,” he told reporters.

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 referred requests for comment to the South Korean military.

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.”

Moon Sung-mook, a senior military expert at the Korea Research Institute for National Strategy in Seoul, said it was unclear whether the issue was with the bombs themselves, a maintenance problem, a fault with the aircraft or human error.

“It will take some time to determine the exact cause, but it is important to analyze the cause and establish preventive measures,” he told NBC News in an interview.

Stella Kim reported from Seoul and Peter Guo reported from Hong Kong.