Stanford experts examine options for USA in dealing with North Korea

China's official Xinhua News Agency had earlier designated the magnitude-3.4 quake in North Korea as a possible result of an explosion.

China will restrict oil exports to and ban textile imports from North Korea, the commerce ministry announced on Saturday, as Beijing joined global efforts to enforce tighter UN Security Council sanctions on Pyongyang for its provocative nuclear and missile tests.

South Korea's weather service has rejected a claim that a recent quake in North Korea was caused by an explosion, saying it was a natural tremor. "In this case we saw none".

Kim Dong-yub, a former South Korean military official who is now an analyst at Seoul's Institute for Far Eastern Studies, said it's more likely that the North's next significant launch would be a full-range test of an unarmed Hwasong-14 ICBM.

However, initial assessment of the quake differed widely, with the Chinese natural disaster administration saying that it had detected a magnitude 3.4 natural disaster in North Korea that was a "suspected explosion".

Atmospheric tests of nuclear-armed missiles, as NPR's Geoff Brumfiel reported, are risky for a host for reasons, including the potential for sending nuclear fallout in unpredictable patterns and, if a test were to be administered by North Korea, in the direction of the U.S.

But the country's quake monitoring centre later went on the say a magnitude 3.4 natural disaster was not the result of a fresh missile test.

A second tremor soon after that test was possibly caused by a "cave-in", CENC said at the time.

North Korea's foreign minister later said that could be a hydrogen bomb test in the Pacific Ocean if Kim orders it.

The U.S. Geological Survey said it could not conclusively confirm whether the quake, which it measured at magnitude 3.5, was man-made or natural.

Wang Yi also told the annual U.N. General Assembly that China was committed to the denuclearization of the Korean Peninsula and there should be no new nuclear weapons north or south of the border, or elsewhere in Northeast Asia. Website 38 North said satellite imagery taken after that test appeared to show landslides atop the site that were more numerous and widespread than after the previous five tests.

U.S. bombers and fighter jets have flown along the coast of North Korea in a show of force.

U.S. Secretary of State Rex Tillerson appealed to the worldwide community, especially Russian Federation and China, to stop the spread of nuclear weapons, calling North Korea a case study of the failure to prevent rogue states from obtaining weapons of mass destruction. The companies have been "ordered to earn foreign currency" and, with legal means of doing so being constrained by United Nations export bans, they "are turning to drugs manufacturing on an industrial scale".

South Korea's weather agency, however, offered a different view.

The strength of the quake was much lower than the tremors registered during any of North Korea's previous nuclear tests, including its first detonation in 2006, which triggered a 4.1-magnitude quake.

Secretary of State Rex Tillerson says North Korea's Kim Jong Un is "being tested" by the strongest sanctions ever put in place by the US and the worldwide community.