A Navy patrol aircraft crashed on a mountain in the southeastern city of Pohang on Thursday, killing all four people onboard.

According to the Navy and firefighting authorities, the P-3C maritime patrol plane crashed at around 1:50 p.m., six minutes after a liftoff from the Pohang naval base for training, with the cause still yet unknown.

Firefighters were dispatched to extinguish a fire that broke out at the accident site.

The Navy later announced the four yet-to-be identified people onboard were found dead.

While the passengers included a lieutenant commander-level pilot, a naval captain and two noncommissioned officers, no civilian casualty was reported from the crash.

Acting President Lee Ju-ho, meanwhile, ordered authorities to exert full efforts to swiftly conduct an investigation to prevent further damage.