North American Aerospace Defense Command officials said North Korea appeared to have successfully launched an object in orbit on a missile, marking a technological success for the hermit nation.

North Korea had confirmed hours earlier the launch of a long-range rocket on Wednesday and said it had succeeded in its mission of placing a satellite into orbit.

A previous launch of the same Unha-3 rocket in April had ended in failure, with the carrier exploding shortly after take-off.

"North American Aerospace Defense Command officials acknowledged today that US missile warning systems detected and tracked the launch of a North Korean missile at 7:49 pm EST" (0049 GMT Wednesday), the joint US-Canadian agency said in a statement. "The missile was tracked on a southerly azimuth."

NORAD said early indications suggested that the first stage of the rocket fell into the Yellow Sea, and estimated that the second stage fell into the Philippine Sea.

"Initial indications are that the missile deployed an object that appeared to achieve orbit," it added. "At no time was the missile or the resultant debris a threat to North America."

Washington and its allies have long insisted such launches are disguised tests for an intercontinental ballistic missile capable of carrying a nuclear warhead.

Last week, the head of the US Pacific Command said Washington had deployed naval ships equipped with ballistic missile defenses and was monitoring North Korea "very closely" ahead of the anticipated launch.

Two guided missile destroyers, the USS Benfold and the USS Fitzgerald, had been sent to the area ahead of the launch, a Navy official said.

The two ships were moving in to "monitor any potential missile launch by North Korea and to reassure regional allies should a launch occur," said the official, who spoke on condition of anonymity.

Both destroyers are equipped with the sophisticated Aegis ballistic missile defense system.

The U.N. Security Council was set to hold consultations Wednesday after the launch, at the request of Japan and the United States, a Western diplomat said.

U.N. resolutions 1718 and 1874 ban Pyongyang from any nuclear or ballistic activity. (AFP)