North Korea on Tuesday said it had conducted a “successful” underground nuclear test, a move that brought condemnation from its neighbours and threatened to heighten regional tensions.

The state-run Korean Central News Agency said a “miniaturised” nuclear device had been detonated successfully… “in a safe and perfect manner.” It said the test — the third conducted by the country since 2006 and the first under the new leader Kim Jong-un — was a response to “outrageous” American hostility and the sanctions imposed on the country for a rocket launch in December.

“By origin, the Democratic People’s Republic of Korea had neither need nor plan to conduct a nuclear test,” an official statement said. “But the DPRK’s patience reached its limit as the U.S. intensified such hostile acts.”

The test was reported to have taken place at a site in the North Hamgyeong province, where the Punggye-ri nuclear complex that conducted tests in 2006 and 2009 is located. The 2009 test brought tighter sanctions from the United Nations Security Council.

Tuesday’s test brought quick condemnation. U.N. Secretary-General Ban Ki-moon said it was “a clear and grave violation of the relevant Security Council resolutions.” South Korea said it represented an “unacceptable threat,” while U.S. President Barack Obama described it as “a highly provocative act”.