Speaking with reporters ahead of a Wednesday emergency meeting of the UN Security Council at the UN headquarters in New York, Ban said the test was "deeply troubling,” "profoundly destabilizing for regional security" and in “contravention of the international norm” against such activities.
"This test once again violates numerous Security Council resolutions despite the united call by the international community to cease such activities," he said.
Elsewhere in his comments, the UN chief called on Pyongyang to cease any further nuclear tests and fulfill its obligations for "verifiable denuclearization."
The remarks came hours after North Korea’s state-owned broadcaster, the KCTV, reported that Pyongyang had successfully conducted its first hydrogen bomb test on Wednesday morning.
North Korea’s state news agency later said in a statement that Pyongyang would continue to develop its nuclear program as a means of deterrence against potential acts of aggression from the United States.
Meanwhile, the US Geological Survey had reported an artificial earthquake in the region earlier on Wednesday, saying that the epicenter of the quake was about 50 kilometers (30 miles) northwest of the city of Kilju, which serves as the seat of North Hamgyong Province, and next to the Punggye-ri nuclear test site.
NATO, Germany, Japan, South Korea, the United States, Britain and France have all denounced the hydrogen bomb test, saying it clearly violates resolutions by the UN Security Council and undermines regional and international security.
China, Pyongyang’s main ally, also stressed that it was “resolutely” opposed to the test and would call in North Korea’s ambassador.
North Korea declared itself a nuclear power in 2005 and carried out several nuclear weapon tests in 2006, 2009 and 2013.
The Communist state is under UN sanctions over launching missiles considered by the US and South Korea as ballistic and aimed at delivering nuclear warheads, but Pyongyang says its numerous missile tests seek to boost its defense capabilities in the face of enemy threats.
North Korea has repeatedly said joint military maneuvers by South Kora and the US pose direct threats against its security.