The long-range missile was thought to be a Taepodong 2 and failed about 35 seconds after launch, US state department officials said on Wednesday.

Though the Pentagon confirmed that six missiles had been launched, South Korean officials said North Korea tested 10 short-, medium- and long-range missiles.

John Bolton, the US ambassador to the United Nations, said the United States was "urgently consulting" other Security Council members about the launches.

US officials said the North Korean military first fired two Scud-type short-range missiles that landed in the Sea of Japan and then the Taepodong 2 that "failed early in flight".

Three more launches were detected later.

Stephen Hadley, the US national security adviser, said the launch was not a threat to the United States, but the tests were considered "provocative behaviour".

Shinzo Abe, the Japanese chief cabinet secretary, described the launches as "a grave problem in terms of peace and stability".

Criticised

"Today's launches were done despite advanced warning by the  relevant countries," he said.

"This is a grave problem in terms of peace and stability not only of Japan but also of international society. We strongly protest against North Korea."

The Taepodong 2 is said to be a multi-stage missile with a possible range of 3,500km to 4,300km, which could put parts of Alaska in range - the cause of US concerns.

George Bush, the US president, and Junichiro Koizumi, the Japanese prime minister, had warned North Korea against test-firing a long-range missile.

Last week, Bush spoke of a harsh US response if North Korea went ahead with such a launch.

The South Korean government called a ministerial meeting in response to the tests.