The drills -- the first such exercises since 2019 -- come after a record-breaking blitz of weapons tests by Pyongyang this year, including firing an intercontinental ballistic missile at full range for the first time since 2017.

The training, which runs to July 29, is being carried out at the Rodriguez Live Fire Complex, close to the heavily-fortified Demilitarised Zone (DMZ) between North and South Korea, the US 2nd Infantry Division told AFP.

The drills ensure US air crews "are qualified on their Apaches, maintain their proficiency on their helicopters, and are capable of executing their mission if called upon," a spokesperson said in a statement sent to AFP.

According to local reports, the US military stopped using the Rodriguez Live Fire Complex in Pocheon in 2018 due to complaints from local residents about noise and safety.

The ongoing drills are understood to be for "noise measurement", an official from Seoul's defence ministry said, apparently referring to locals' concerns over the disruption.

But the two countries, long-time regional security allies, said in May that they were looking to ramp up joint military exercises, which had been scaled back due to Covid-19, and during a bout of failed diplomacy with the North.

South Korea's hawkish new President Yoon Suk-yeol -- who took office in May -- has vowed a tougher stance against Pyongyang, vowing to "normalise" US-South Korea joint military drills.

Such exercises have always infuriated the North, which considers them rehearsals for invasion.

The US is using its advanced AH-64E v6 Apache helicopters in the drills, according to images tweeted by the US 2nd Infantry Division.

"5th Squadron, 17th Cavalry Regiment and 4-2 Attack Battalion are conducting aerial gunnery, certifying their crews on AGM-114 Hellfire missiles, Hydra 70 rockets and 30mm canon," it said.

Washington and Seoul officials have repeatedly warned that the North is preparing to carry out what would be its seventh nuclear test -- a move that the United States warned would provoke a "swift and forceful" response.

A total of six US top-of-the-line F-35A fighters also arrived in the South earlier this month for a 10-day allied exercise that took place until July 14.

It was the first public deployment of American stealth warplanes in the country since late 2017.