Two trainer aircraft of South Korea's air force collided in mid-air on Friday, authorities said, with media putting the casualties at three pilots killed and another injured in the rare accident.
The crash took place near the KT-1 aircrafts' base in the southeastern city of Sacheon at about 1:35 p.m. (0435 GMT), the air force said in a statement, adding that it was checking for any deaths.
Citing fire officials, the Yonhap news agency said three pilots were killed and another seriously injured.
More than 30 firefighters and rescuers have begun a search at the crash site, it added.