North Korea lambasted the U.S. on Tuesday over the staging of what it called a "nuclear bomb-dropping drill" by flying a two B1-B strategic bombers close to its border with the South a day earlier.

In a report by the state-run Korean Central News Agency, the North claimed the B-1B bombers, which are currently deployed to Guam, flew over South Korea and approached an area 80 km east of Gangneung, an eastern city near the Military Demarcation Line that serves as the border between the two Koreas.

Moon Sang-gyun, a spokesman for the South Korean Defense Ministry, said the exercise took place on Monday but declined to give further details, Reuters reported Tuesday.