Two US B-1 bombers have flown over South Korea in response to North Korea's recent ballistic missile tests.

Under the command of US Pacific Air Forces, the two B-1s took off from Andersen Air Force Base in Guam on Saturday.

The bombers were then joined by Japanese and South Korean fighter jets and flew over the Korean Peninsula and over the Osan Air Base in South Korea.

A US Air Force B-1B Lancer assigned to the 9th Expeditionary Bomb Squadron, deployed from Dyess Air Force Base, Texas, prepares for a 10-hour mission from Andersen Air Force Base, Guam, into Japanese airspace and over the Korean Peninsula, July 30, 2017. (Photo by AFP)

Their 10-hour mission, which included formation and intercept training, was in direct response to Pyongyang’s successful test of an intercontinental ballistic missile (ICBM) on Friday and the previous July 3 launch of the "Hwansong-14" rocket, according to a statement by the US Air Force.

“North Korea remains the most urgent threat to regional stability," General Terrence O'Shaughnessy, a Pacific Air Forces Commander, said in the statement on Saturday.

"Diplomacy remains the lead; however, we have a responsibility to our allies and our nation to showcase our unwavering commitment while planning for the worst-case scenario. If called upon, we are ready to respond with rapid, lethal and overwhelming force at a time and place of our choosing," he added.

This July 28, 2017 picture released from North Korea's official Korean Central News Agency (KCNA) shows North Korea's intercontinental ballistic missile (ICBM), Hwasong-14 being launched at an undisclosed place in North Korea. (Photo by AFP)

On Saturday, North Korean leader Kim Jong-un said the whole US mainland was now within the range of the newly-tested guided missile, an updated version of the Hwasong-14 ICBM that flew as far as 998 kilometers for some 47 minutes at a maximum altitude of 3,724.9 kilometers.

According to North Korea's official Korean Central News Agency (KCNA), Kim, who himself oversaw the second ICBM test, said the long-range missile demonstrated the country's surprise attack capability and sent a "serious warning" to the United States.

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Following the test, US authorities confirmed that the missile was an ICBM, but downplayed claims that it could reach the US mainland.

Meanwhile, the Russian Defense Ministry, in a statement, cast doubt on the declared nature of the missile and said its characteristics appeared to be "those of a medium-range ballistic missile."

In response to the test, the US and South Korea also conducted a military exercise later on Friday, using surface-to-surface missiles.

The US 8th Army said the drill by its troops and the South Korean army was carried out to show their "precision firing capability" and "exercise assets countering North Korea's missile launch."