Ban Ki-moon called the underground nuclear test "deeply troubling" and "profoundly destabilizing for regional security."
UN Secretary-General Ban Ki-moon on Wednesday denounced North Korea's nuclear test and called on Pyongyang to halt its nuclear program.
"I condemn it unequivocally. I demand the DPRK cease any further nuclear activities," Ban told reporters ahead of an emergency meeting of the UN Security Council.
North Korea said it had carried out a "successful" miniaturized hydrogen bomb test -- a shock announcement that, if confirmed, would massively raise the stakes in the hermit state's bid to strengthen its nuclear arsenal.
Ban called the underground nuclear test "deeply troubling" and "profoundly destabilizing for regional security."
He stressed that it was in violation of numerous Security Council resolutions barring Pyongyang from engaging in nuclear activities.
Three previous tests in 2006, 2009 and 2013 triggered waves of UN sanctions.