US supersonic B-1B Lancer bombers conduct exercise over South Korea ahead of Donald Trump visit to Asia

Days before US President Donald Trump tour to Asia that will include South Korea and is set to be dominated by the North Korean nuclear issue, US bombers overflew the Korean peninsula on Thursday as part of an exercise with Japanese and South Korean warplanes.

Flights by supersonic B-1B Lancer bombers in the area always enrage North Korea, which condemned the drill as "blackmail" early Friday. In recent months, Pyongyang's tested ballistic missiles and atomic programmes which raises tensions in the region. 

According to the US Pacific Air Force statement, two B-1B aircraft took off from Andersen Air Force Base in Guam and were joined west of Japan by Japan Air Self-Defense Force fighters.

"The Lancers then transited overland to Korea to integrate with Republic of Korea fighters in the Yellow Sea," the statement read, adding that the aircraft later returned "to their respective home stations."

The operation follows an October 10 "show of force" in which two Lancers staged the first night-time joint aviation exercises with Japan and South Korea.

Trump and North Korean leader Kim Jong-Un have exchanged threats and personal insults in recent months -- the US president has warned of "fire and fury" in response to Pyongyang's threats, and the North's KCNA news agency this week called him "incurably mentally deranged".

North Korea in July launched two intercontinental ballistic missiles apparently capable of reaching the US mainland -- described by Kim as a gift to "American bastards".

It followed up with two missiles that passed over Japan, and its sixth nuclear test, by far its most powerful yet.Pyongyang may be preparing for another missile test, Seoul's spy agency report said Thursday.

The North habitually condemns B1-B flights as rehearsals for an attack, and KCNA said Friday: "The reality clearly shows that the gangster-like US imperialists are the very one who is aggravating the situation of the Korean peninsula and seeking to ignite a nuclear war."

Trump will start Asian tour on Friday.