Defying the wishes of a number of nations, North Korea launched a controversial long-range rocket over Japan, a move U.S. President Barack Obama called a "provocative act" that will further isolate the nation.

The U.S. State Department, Japanese and South Korean government officials confirmed the launch. The UN Security Council approved an emergency session for Sunday afternoon in New York following a request from Japan that came immediately after the launch.

Liftoff took place Sunday morning from the coastal Musudan-ri launch pad in northeastern North Korea, the South Korean and U.S. governments said.

Western countries fear that the launch is a cover for a ballistic missile test for the North, which has nuclear weapons, and  violates a 2006 resolution barring the regime from ballistic missile activity.

But North Korea has claimed the launch was to send an experimental communications satellite into orbit as part of a peaceful bid to develop its space program.

"With this provocative act, North Korea has ignored its international obligations, rejected unequivocal calls for restraint, and further isolated itself from the community of nations," Obama said in a statement from Prague.

"I urge North Korea to abide fully by the resolutions of the UN Security Council," Obama said.

Obama cautioned that North Korea will not find acceptance in the international community "unless it abandons its pursuit of weapons of mass destruction."

The president said the rocket was a Taepo-dong 2 missile, a three-stage rocket with potential range of more than 6,600 kilometres.

Japanese broadcaster NHK cited the Japanese government as saying the rocket flew over Japan. Japan said the rocket's second booster stage had splashed down in the Pacific Ocean, Reuters reported.

But there were no reports of any debris falling on Japan.

South Korea's presidential Blue House said the launch poses a "serious threat" to stability on the Korean peninsula and that it would respond to the provocation "sternly and resolutely."

North Korea earlier advised international authorities the launch would take place between Saturday and Wednesday, between 11 a.m. and 4 p.m. local time.

Saturday was to be the start of a five-day window during which North Korea said it would send a communications satellite into space from a launch pad in Musudan-ri.

With files from the Associated Press