North Korea said Tuesday that it had conducted a new, more powerful underground nuclear test using more sophisticated technology, jolting the already fragile security situation in Northeast Asia and drawing condemnation from around the globe. The test, "probably" conducted in the vicinity of P'unggye, yielded "several kilotons," according to assessments cited by the U.S. director of national intelligence. It is the first nuclear test carried out under the North's young leader, Kim Jong Un, who appears to be sticking closely to his father's policy of building up the isolated state's military deterrent to keep its foes at bay, shrugging off the resulting international condemnation and sanctions.