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 USA and the global community.
But Japan's Kyodo News earlier reported that a 3.4 magnitude natural disaster was detected at a depth of zero kilometres near the North's nuke test site, citing China's quake agency.
The U.N. sanctions were a response to North Korea's sixth nuclear test, which experts said was its biggest by far, earlier this month.
Imports of textiles from North Korea would also be banned immediately, the statement said.
The United States Geological Survey was neutral in its assessment on the cause of the tremor, which it recorded as a 3.5 magnitude quake, saying in a statement that it could not "conclusively confirm at this time the nature (natural or human-made) of the event".More news: Julia Louis-Dreyfus Sets Her Place in TV History, Again
North Korea has launched dozens of missiles this year, several flying over Japan, as it accelerates its program aimed at enabling it to target the United States with a nuclear-tipped missile.
In a rare direct statement, Kim said that Trump would "pay dearly" for the threats, and that North Korea "will consider with seriousness exercising of a corresponding, highest level of hard-line countermeasure in history".
"It could be a natural quake that really was man-made as the nuclear test would have transferred a lot of stress", he said.
The secretary of state defended Trump's blunt rhetoric in his speech to the U.N. General Assembly in NY on Tuesday, in which the president threatened to "totally destroy" North Korea if the United States is "forced to defend itself or its allies", prompting astonished gasps from some in the audience. The larger one had a 3.4 magnitude, the group's initial assessment found, which is much smaller than anything declared as a nuclear test in previous years.
But on the fringes of the United Nations meeting this week, North Korean Foreign Minister Ri Yong Ho upped the tensions further, telling reporters Pyongyang might now consider detonating a hydrogen bomb outside its territory.More news: Saudis call on Myanmar to allow Rohingyas to return
North Korea's foreign minister said this week that his country could test a powerful nuclear weapon over the Pacific Ocean in response to President Donald Trump's threats of military action.
He said sanctions would have no effect on Pyongyang's resolve to develop its nuclear weapons, with the ultimate goal being "balance of power with the US". "Negotiation is the only way out and deserves every effort", Wang told the UN General Assembly.
The UN Security Council voted on September 11 to limit fuel supplies and ban the North's textile exports. "We have developed strong allies and strong alliances internationally".
North Korea's state-run Korean Central News Agency published articles Saturday with comments slamming Trump.
Prohibition of the imports of North Korean textiles should be carried out immediately from the date of announcement, and for the volume of transactions that have been concluded prior to the passage of the United Nations resolution, the import procedure must be completed by December 10, the ministry said.More news: Liverpool: If Danny Ward excels he should play in the Premier League