North Korea has launched a long-range missile but the rocket has failed and crashed into the sea, according to reports.
Officials in South Korea said the rocket broke into pieces and crashed a few minutes after takeoff.
"South Korean and US intelligence understand that North Korea's missile launch failed," a spokesman for the South's defence ministry told reporters at a briefing, adding that Seoul would make an additional announcement after final confirmation.
Japan's defence minister said that a "flying object" that fell into the ocean after a short flight.
"We have the information some sort of flying object had been launched frol North Korea," defence minister Naoki Tanaka told reporters.
"The flying object is believed to have flown for more than one minute and fallen into the ocean. This does not affect our country's territory at all."
Sky’s Asia correspondent Holly Williams, reporting 30 miles from the launch site, said: "The three-stage rocket was supposed to carry a weather satellite into space.
"What will be interesting is if North Korea admits it failed or insist it was a success."
North Korea launch programme has drawn international criticism due to concerns it could further the reclusive state's ability to deliver a nuclear warhead.
German foreign minister Guido Westerwelle called for a "strong" response from the UN Security Council.
"I condemn the attempt for a rocket launch by North Korea. This is a violation of international obligations and will increase tensions on the Korean peninsula," Mr Westerwelle said.
"The Security Council of the United Nations must give a strong answer to this violation of international law."
The security council will meet later today to discuss a possible response to North Korea's rocket launch, diplomats have confirmed.