The US, Japan and South Korea say it flew only for a short time before breaking up and crashing into waters off the Korean peninsula. North Korea said its scientists were assessing what had caused the failure.
North Korea says the aim of the rocket was to launch a satellite into orbit - a move marking the 100th anniversary of the birth of national founder Kim Il-sung. But the US and other nations say the launch constituted a disguised test of long-range missile technology banned under UN resolutions.
In a statement, the White House condemned the launch, despite its failure. The UN Security Council is due to meet later in the day to discuss the launch. China, North Korea's closest ally, has called for calm and restraint on the Korean peninsula.
'Ended in failure'
The rocket went up at 07:39 local time (22:39 GMT Thursday), South Korean officials said.
Its intended flight path would have taken it south, to the west of the Korean peninsula between Japan and the Philippines. Both Japan and South Korea had threatened to shoot it down if it threatened their territory.
But officials from several nations observing the launch said the rocket had failed.
"Initial indications are that the first stage of the missile fell into the sea 165km (105 miles) west of Seoul, South Korea," the North American Aerospace Defense Command (Norad) said in a statement.
"The remaining stages were assessed to have failed and no debris fell on land. At no time were the missile or the resultant debris a threat."
Japan reported similar details.