South Korea and the United States kicked off their first large-scale joint air drills in nearly five years, with more than 240 aircraft mobilized, including their advanced stealth jets, as the allies strive to bolster deterrence against evolving North Korean threats, according to officials here.

The Vigilant Storm exercise will run through Friday over the sky of the Korean Peninsula amid concerns that Pyongyang could may soon carry out a nuclear test. The North may also try to show its own firepower with the firing of ballistic missiles or artillery shells in response to the allies' drills.

The South is deploying some 140 planes, including F-35A stealth fighters, and F-15K and KF-16 jets, while the US is dispatching about 100 assets, including F-35B stealth fighters based in Okinawa, Japan, and EA-18 electronic warfare aircraft, as well as KC-135 tankers and the U-2 high-altitude reconnaissance aircraft.

The allies plan to perform a total of more than 1,600 sorties during the drills, with the Korean Air and Space Operations Center operating the forces to enhance operational capabilities.

The Australian Air Force is taking part in the practice as well, with a KC -30A multi-role tanker transport.

South Korea and the US launched such a major combined air training program in 2015 under the name of Vigilant ACE, but it had been held every year until late 2017, when the then Moon Jae-in administration staged a proactive campaign for inter-Korean reconciliation.

This year's exercise comes after a series of provocations by Pyongyang in recent weeks, including its firing of two short-range ballistic missiles into the East Sea on Friday. (Yonhap)