Unspecified U.S. military sensors detected and tracked North Korea’s three-stage Taepo Dong-2 missile as it flew out over the Yellow Sea before breaking up shortly after liftoff, according to a North American Aerospace Defense Command (NORAD) press release.

The first stage of the missile, which launched at 6:39 p.m. EDT April 12, fell into the sea about 165 kilometers west of Seoul, South Korea, according to the press release. The rocket’s other two stages failed to ignite and no debris fell on land, NORAD said.

“At no time were the missile or the resultant debris a threat,” the press release said.

White House spokesman Jay Carney nonetheless characterized the launch as a threat to regional security and a violation of international law.

“While this action is not surprising given North Korea’s pattern of aggressive behavior, any missile activity by North Korea is of concern to the international community,” Carney said in the statement. “The United States remains vigilant in the face of North Korean provocations, and is fully committed to the security of our allies in the region.”

Riki Ellison, founder of the Missile Defense Advocacy Alliance in Washington, said the all-liquid-fueled rocket completed burnout of its first stage about 100 seconds into flight at an altitude of roughly 70 kilometers. The second stage appeared not to ignite and along with the third stage fell harmlessly into the Yellow Sea, Ellison said in an April 13 press release.

“The United States missile defense sensor assets located in the region both on sea, land and in space tracked the missile from its launch to its breakup,” Ellison said. Much of the debris caught fire and exploded during the descent, he said.

North Korea said its intent was to launch an Earth observing satellite into orbit, but outside experts suspect the real purpose was to test a long-range missile. North Korea has conducted two other tests of comparable vehicles since 1998, with both of those flights ending in failure as well.