A nuclear-capable B-52 bomber flew over an air base in South Korea in a move that was both a training mission and a show of force.
The low-level flight was conducted as a demonstration of U.S. commitment to South Korea, in response to a nuclear test by North Korea, the U.S. Pacific Command said in a statement.
"The bomber, which is capable of carrying nuclear weapons, was accompanied by two fighter planes from the U.S. and South Korea," NPR's Elise Hu reports from Seoul.
"This move follows last Wednesday's nuclear test by the north, which North Korea claims was a hydrogen bomb," Elise says. "The testing set off a barrage of international criticism, and policymakers are considering what action to take next."
Tensions between South Korea and North Korea have been running high since the test.
On Friday, South Korea resumed cross-border propaganda broadcasts, Elise reported. The broadcasts — which typically include news, weather, anti-North Korea messages and K-pop — are seen as an act of aggression by the North.