A Russian warplane reportedly entered South Korea's Air Defense Identification Zone, or KADIZ, on Tuesday.
A government source said that the Air Force deployed a fighter jet after an aircraft, presumed to be a Russian military plane, entered the KADIZ over the East Sea.
South Korea reportedly dispatched an F-15K fighter jet to expel the foreign aircraft.
The reported incursion comes after a Russian warplane entered Korean airspace near the Dokdo islets for seven minutes on July 23, prompting warning shots from South Korea.
A Russian warplane is known to have violated the KADIZ on August 8 as well.