President Moon Jae-in on Thursday expressed his condolences over the death of three firefighters who were killed while battling a warehouse blaze in Pyeongtaek.

Moon said he is "heartbroken" by the news of three firefighters "who died while engaging in rescue activities at the forefront of protecting the lives and safety of people," according to presidential spokesperson Park Kyung-mee.

Moon prayed for the repose of the deceased and offered deep consolation to families of the victims, Park said in a statement.

The fire at the seven-story warehouse in Pyeongtaek, 70 kilometers south of Seoul, was first reported Wednesday. Authorities reportedly brought the blaze under control Thursday morning but the fire suddenly began to rise again later.

The three victims at the warehouse fire scene were unaccounted for on Thursday morning and their bodies were found later. (Yonhap)