SEOUL - South Korea and the United States kicked off their largest-ever joint air drill on Friday at a time of elevated military tensions with North Korea.
The so-called "Max Thunder" exercise, which is held twice a year, will last until April 25 and involve 103 aircraft and 1,400 service personnel, a South Korean air force spokesman said.
"In numerical terms, it's the largest exercise of its kind that we've done," the spokesman told AFP.
The last Max Thunder drill held in October-November last year involved 97 aircraft and some 1,000 troops.
Seoul's F-15K jet fighters will take part along with US Air Force F-15 and F-16s and US Marines' FA-18 and EA-18 aircraft.
"The combined air forces will strengthen their battle readiness under the current situation when tension rises over the Korean peninsula," a South Korean air force statement said.
The exercise will focus on "practical scenarios" involving precision attacks on enemy positions and supply-drop missions for troops infiltrating enemy territory.
It comes as the allies are winding up separate annual military drills which began late February, and have been denounced by Pyongyang as rehearsals for invasion.
In a pointed protest at the exercises, Pyongyang carried out a series of rocket and missile launches, capped by its first mid-range missile test since 2009 on March 26.
The two Koreas also traded artillery fire across the tense Yellow Sea border on March 31, after the North dropped around 100 shells across the maritime boundary during a live-fire drill.
The exchange followed a North Korean warning that it might carry out a "new" form of nuclear test - a possible reference to a uranium-based device or a miniaturised warhead small enough to fit on a ballistic missile.
The United States, South Korea and Japan, meeting in Washington on Monday, condemned the ballistic missile tests and urged the North "to refrain from further threatening actions".