The U.S. Air Force conducted another flight of B-1B long-range bombers near the Korean peninsula on Thursday, escorted by fighters from South Korea and Japan. North Korea responded with predictable outrage, accusing the “gangster-like U.S. imperialists” of practicing for a nuclear surprise attack.

American B-1B bombers made another “show of force” flight over South Korea on Tuesday, escorted by F-15 fighters from the South Korean military.

In a briefing to reporters outside the U.N. Millennium Plaza Hotel in New York City on Monday, North Korea’s Foreign Minister Ri Yong-ho threatened to shoot down U.S. strategic bombers even when they are flying outside of North Korean airspace.

South Korean fighter jets are scheduled to train with two American B-1B Lancer supersonic bombers on Tuesday, a demonstration of cooperation and military power at a moment when questions about the new South Korean administration linger and anger at North Korea is mounting over the murder of American college student Otto Warmbier.

The U.S. military confirmed a military exercise by Air Force B-1B Lancer bombers over the South China Sea Thursday, a move that prompted Beijing, which illegally claims most of the sea, to remind Washington that it remains “vigilant” before U.S. exercises.