China's official Xinhua news agency said the epicentre was roughly at the same place as a similar shallow quake on Sept 3, which turned out to be caused by North Korea's sixth and largest nuclear test.
South Korea's meteorological agency said early indications suggested it was a natural quake because no soundwaves specific to man-made tremors had been identified.
North Korea warned Sunday that military action by the United States would lead to the "most tragic" end for the USA, vowing that the country would not sit on President Donald Trump's threat to destroy the regime.
The US president, the foreign minister said, would "pay dearly" for his speech, in which he also said he would "totally destroy" North Korea if the US was forced to defend itself or its allies.
Earlier on Saturday, China said it will limit exports of refined petroleum products from October 1 and ban exports of condensates and liquefied natural gas immediately to comply with the latest United Nations sanctions.
"The USGS said that their seismologists confirmed it happened at a depth of 5KM and said, We can not conclusively confirm at this time the nature [natural or human made] of the event".
As The Two-Way reported, the tremor occurred near the site where North Korea conducted its most powerful nuclear test earlier this month.
North Korea's nuclear tests to date have all been underground, and experts say an atmospheric test, which would be the first since one by China in 1980, would be proof of the success of its weapons program. It said the operation showed the seriousness with which it took North Korea's "reckless behavior".
Nuclear tests have earlier caused earthquakes in the Communist-dominant country.
Trump blasted Pyongyang in his U.N. General Assembly speech last week, and began referring to Kim as "Rocket Man" on Twitter and at a rally Friday. Ri, who said Pyongyang's ultimate goal was to establish a "balance of power with the US", retorted that Trump himself was on a "suicide mission" after the U.S. president said Kim was on such a mission. "S. dotard with fire".
Harsh sanctions placed on North Korea's trade with the outside world will have no impact on its ability to complete building a nuclear bomb capable of reaching the United States, Ri said, suggesting that stage is imminent.
A ban on textile imports from the North will go into effect immediately, the statement said.
He tweeted: 'Just heard Foreign Minister of North Korea speak at U.N. If he echoes thoughts of Little Rocket Man, they won't be around much longer!'
On September 15, North Korea launched a medium-range ballistic missile over Japanese territory - several days after the adoption of UN Security Council Resolution 2375.