Mid-air crash in South Korea kills four

The crash happened about 6km south of the KT-1 airplanes' base in the southeastern city of Sacheon, at about 1.37pm on Friday, the air force said.

"Despite their attempts at an emergency escape ... all of the two student pilots and two flight instructors aboard the two planes died," it said in a statement.

The air force said there were no civilian casualties but had formed a team to determine the cause of the accident and damage, including on the resident community.

The crash site is located in a largely agricultural area, and photos published by Yonhap showed smoke rising from a mountain, and one car shattered by fragments of the aircraft while being parked in front of a farmhouse.

The KT-1 is a single-engine basic trainer and light attack aircraft jointly built by the state-run Agency for Defence Development and a contractor, Korea Aerospace Industries.