South Korea and the United States conducted combined air drills, involving at least one US B-52H strategic bomber, over the Korean Peninsula on Thursday, Seoul's Joint Chiefs of Staff said, a day after North Korea fired an intercontinental ballistic missile.

The North's state media has confirmed the country fired a solid-fuel Hwasong-18 ICBM on Wednesday, raising tensions already heightened by the North's accusations earlier this week claiming US military spy aircraft "intruded" into the area over its exclusive economic zone.

The South deployed F-15K fighters to the drills, while the US also sent F-16 jets, the JCS said, without specifying where in the peninsula the exercise took place.

"Through this exercise, South Korea and the United States enhanced combined operational capabilities through the swift deployment of the US extended deterrence asset that was coordinated in a timely manner," the JCS said in a release.

It said the drills demonstrated the US' resolve to carry out its "extended deterrence" commitment, adding that the South Korea-US alliance will continue to realize "peace through strength" based on their "overwhelming" capabilities.

Extended deterrence refers to America's commitment to using the full range of its military capabilities, including nuclear, to defend its ally.

The US pledged to enhance the "regular visibility" of strategic assets on the Korean Peninsula in a joint declaration issued by President Yoon Suk Yeol and US President Joe Biden during their summit in Washington in April. (Yonhap)