The incident occurred at 09:30 a.m. Jakarta time in Sagara village, Garut Regency. The victims included four soldiers and nine residents, said Brigadier General Wahyu Yudhayana, spokesperson for the Indonesian Army.
"Four personnel of the Indonesian Army and nine members of the community were killed," he told a press conference, Xinhua reported.
"The detonations in two holes were successfully conducted. However, when the team was preparing detonators in the third hole, an unexpected explosion occurred, killing four soldiers and nine residents," he explained.
Yudhayana noted that the army team had previously inspected all equipment and confirmed they were in safe condition. Additionally, the site had been routinely used for disposing of expired ammunition.
All victims were taken to Pameungpeuk General Hospital, the spokesman said.
An investigation will be conducted to determine the cause of the fatal incident, Yudhayana added.