The B-1 Lancer strategic bombers took off from an American base in Guam on Tuesday and performed a low-altitude flight over Osan Air Base, near Seoul, the South's capital.

American and South Korean fighter jets escorted the B-1s during the low-speed flight, which took place 77 km (48 miles) from the Demilitarized Zone border with the North.

General Vincent Brooks, the commander of the 28,500 US troops in South Korea, said the symbolic flight illustrated the strong military alliance between Washington and Seoul.

"Today's demonstration provides just one example of the full range of military capabilities in the deep resources of this strong alliance to provide and strengthen extended deterrence," the American commander said in a statement.

The fly-over came days after Pyongyang conducted its fifth and biggest “nuclear warhead explosion” test on Friday, which, according to South Korea’s meteorological agency, was almost identical to America’s nuclear bombing of Hiroshima in 1945.

The test intensified an ongoing military standoff between the US and North Korea, which was ignited by Washington’s deployment of sophisticated weaponry to the South.

North Korea has pledged to develop a robust nuclear arsenal to protect itself from the US military. Washington, in turn, has stepped up its military presence in the region under the pretext of defending Seoul.

US President Barack Obama rushed to condemn the North’s fifth test, saying Friday that it posed "a grave threat to regional security and to international peace and stability."

He pledged to push for new sanctions against the Pyongyang regime, which has already been hit by five sets of UN sanctions since it first tested a nuclear device in 2006.

It remains to be seen if Obama will succeed in his quest for more sanctions since China, a major supporter of the North, believes such actions can only lead to a dead end, Press TV reported.

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