The 38 North website in the USA, which keeps satellite watch on North Korea, raised its estimate for the yield from the explosion to around 250 kilotons - more than 16 times the size of the device that devastated Hiroshima in 1945.
"It was hard to find out how powerful the nuclear test was with the amount of xenon detected, but we can say the xenon was from North Korea", Choi Jongbae, executive commissioner, told a news conference in Seoul.
"To respond to North Korea by having our own nuclear weapons will not maintain peace on the Korean Peninsula and could lead to a nuclear arms race in northeast Asia", Moon said.
In its first official reaction to the sanctions resolution adopted Tuesday by the U.N. Security Council, North Korea's Foreign Ministry said Wednesday that the sanctions would only strengthen the country's resolve to pursue its nuclear weapons program "at a faster pace without the slightest diversion".
In Seoul, the South Korean government said it was considering providing the North, via United Nations agencies, $8 million in aid for humanitarian assistance for infants and pregnant women, according to the South's Yonhap News Agency.
"The two Prime Ministers condemned in the strongest terms North Korea's continued development of its nuclear weapons and ballistic missile programs, including the latest nuclear test conducted by North Korea on 3 September as well as its uranium enrichment activities", the statement said. A report Thursday in the Nikkei, a Japanese newspaper, said that satellite imagery appeared to indicate that North Korea was preparing for another long-range missile test.
North Korean leader Kim Jong Un is moving mountains with his nuclear tests.
North Korea also uses trusted agents and third party companies located in other countries to facilitate prohibited trade.
This week China reportedly stopped some of its major state-owned banks from providing financial services to new North Korean clients, in what could be a sign of increased sanctions enforcement to prevent any US retaliation.
This figure approaches what 38 North had concluded to be the maximum yield that North Korea's underground Punggye-ri nuclear test site could contain.
The Citigroup representative added: "Not only is the North Korean leader in the process of testing his nuclear weapons (Nuclear - No), scoring the sixth this year but also Donald Trump changes the United States foreign and security policy in a way I have not seen before".