ANKARA

The US, South Korea and Japan on Monday kicked off a key trilateral multi-domain military exercise in what is viewed as their continued efforts to deepen three-way security cooperation against "military threats" from North Korea, according to South Korean media.

The five-day Freedom Edge exercise is being held in international waters off South Korea's southern island of Jeju from Sept. 15 to 19, the Yonhap news agency reported, citing Seoul's military.

"The Freedom Edge exercise is conducted through Friday to strengthen capabilities to deter and respond to North Korea's evolving nuclear and missile threats," Yang Seung-kwan, spokesperson for the Joint Chiefs of Staff (JCS), told reporters.

The ongoing exercise is the third round of the trilateral drills, following previous rounds of the exercise conducted in June and November last year, respectively.

The latest round marks the first such exercise since US President Donald Trump and his South Korean counterpart Lee Jae Myung took office.

The exercise includes training aimed at sharpening ballistic missile defense capabilities, as well as air defense exercises, medical evacuation training and maritime interdiction operation training.

The Freedom Edge exercise coincides with Iron Mace tabletop military exercise between South Korea and the US, which is set to begin also from Monday through Friday.

The drill will focus on integrating Washington's nuclear assets and Seoul's conventional capabilities to deter North Korean threats.

North Korea has protested against joint drills among the three allies.

On Sunday, Kim Yo-jong, the influential sister of North Korean leader Kim Jong-un, condemned the drills and warned the "reckless muscle-flexing" would bring unfavorable consequences.

*Writing by Aamir Latif