Two US supersonic bombers have flown over South Korea, with one of them landing at an air base 40km south of the capital, the second such flight since North Korea's nuclear test this month.
US Forces Korea said the flight by a pair of B-1B Lancer strategic bombers based in Guam was a show of force and of US commitment to preserve the security of the peninsula and the region.
The United States, which has about 28,500 troops in South Korea, flew two B-1 bombers on September 13 escorted by US and South Korean fighter jets in a show of solidarity with Seoul.
The North condemned the earlier flight as an armed provocation that mobilised "ill-famed nuclear killing tools". It did not immediately respond to Wednesday's flight.
The US Air Force said Wednesday's flight was the closest ever to North Korea.
"Today marks the first time the airframe has landed on the Korean peninsula in 20 years, as well as conducting the closest flight near North Korea ever," the US Air Force said on its website which also showed a B-1B bomber landing at the base in South Korea.
The South's Yonhap news agency said the aircraft flew over a US live-fire training site in the Pocheon area bordering the North.
North Korea has ignored global condemnation of its fifth nuclear test on September 9, and this week said it had successfully tested a new rocket engine that would be used to launch satellites, again in violation of UN sanctions.