North Korea routinely denounces the annual military drills as a rehearsal for war. The allies have stressed the exercises are defensive in nature.
The bomber flight came days after North Korea attempted a satellite launch that ended in failure.
The two countries began Ulchi Freedom Shield last week – a joint large-scale military exercise designed to enhance their response to Pyongyang’s nuclear and missile threats, with the second part kicking off on Monday.
Wednesday’s exercise was a demonstration of what the allies have called “extended deterrence” in the face of North Korea’s recent space launch vehicle flights and a show of “strong united defence posture”, South Korea’s defence ministry said in a statement.
On Tuesday in a speech marking Navy Day, North Korean leader Kim Jong Un accused the United States and its allies of increasing the risk of nuclear war, referring to an Aug. 18 summit at Camp David between the United States, South Korea and Japan.
“Owing to the reckless confrontational moves of the U.S. and other hostile forces, the waters off the Korean Peninsula have been reduced to the world’s biggest war hardware concentration spot, the most unstable waters with the danger of a nuclear war,” Kim was quoted as saying by state media KCNA.
(Reporting by Hyunsu Yim. Editing by Gerry Doyle)