North Korea confirmed on Tuesday that it successfully conducted a third nuclear test, the North's KCNA official news agency said.

"It was confirmed that the nuclear test that was carried out at a high level in a safe and perfect manner using a miniaturized and lighter nuclear device with greater explosive force than previously did not pose any negative impact on the surrounding ecological environment," KCNA said.

South Korean, US and Japanese seismic monitoring agencies detected an earthquake with a magnitude between 4.9 and 5.2 at 10:57 am (01:57 GMT) Tuesday prompting speculation that the country had conducted a nuclear test.

Monitoring stations said the quake's epicenter, which was only 1 kilometer deep, was near the site of previous nuclear testing.

UN Secretary General Ban Ki-moon on Tuesday condemned the nuclear test, saying it was "deplorable" that Pyongyang had defied international sanctions.

"The Secretary General condemns the underground nuclear weapon test conducted by [North Korea] today," Ban's spokesman Martin Nesirky said in a statement. "It is a clear and grave violation of the relevant Security Council resolutions."

'Explosion-like' quake

South Korean Defense Ministry spokesman, Kim Min-seok said North Korea gave China and the United States advanced warning that it was planning on conducting a nuclear test.

Japan's public broadcaster NHK reported that the country's meteorological agency said the activity was "different from a normal earthquake."

The head of the UN's Nuclear-Test-Ban Treaty Organization, Tibor Toth, said in a statement that "the event shows clear explosion-like characteristics." Nuclear blasts can create tremors but they are distinct from those caused by natural earthquakes.

North Korea vowed last month to conduct "high-level" nuclear tests in retaliation for tightened UN sanctions following the country's December rocket launch.

The isolated country is banned under UN Security Council resolutions from developing nuclear and missile technology. Tuesday's test is the third time the country has detonated a nuclear device, following previous tests in 2006 and 2009.

The UN Security Council will hold an emergency meeting in New York at 9:00 am EST (1400 GMT) to discuss the nuclear test. South Korea is the president of the 15-nation council this month.

dr,hc/ccp (Reuters, AP, AFP, dpa)