The North Korean aircraft flew north of the so-called tactical action line, north of the Military Demarcation Line between the two Koreas, South Korea's military said in a statement. The virtual line is used as a basis for South Korean air defense operations, a South Korean official said.
South Korea scrambled 80 aircraft, including, F-35A stealth fighters, in response.
A flight of 10 North Korean warplanes made similar maneuvers last month, prompting South Korea to scramble jets.
The maneuvers came after North Korea fired more than 80 rounds of artillery into the sea overnight, and launched multiple missiles into the sea on Thursday, including a possible failed intercontinental ballistic missile (ICBM).
The launches prompted the United States and South Korea to extend air drills that have angered Pyongyang.