Both the US and Japan had said they would consider a range of options - including economic sanctions - if a launch of the Taeopdong-2 missile went ahead.
A state department official called the launch a "provocative act designed to get attention".
"The North Koreans have again clearly isolated themselves," White House press secretary Tony Snow told reporters.
He said President George W Bush had consulted Defence Secretary Donald Rumsfeld, Secretary of State Condoleezza Rice and National Security Adviser Stephen Hadley.
The Assistant Secretary of State Christopher Hill is set to fly out to the region later on Wednesday, while Mr Hadley would be meeting his South Korean counterpart in Washington, in a meeting which had already been scheduled.
Japan's Chief Cabinet Secretary Shinzo Abe said Tokyo "strongly protested" the move by North Korea.
"This is a grave problem in terms of peace and stability not only of Japan but also of international society," he said.
In Seoul, the South Korean government called an emergency cabinet meeting.
Heightened alert
The first missile was launched at 0332 Japan Time (1832 GMT) and crashed into the sea 600 km (373 miles) from the Japanese mainland, the public broadcaster NHK TV said.
The second was fired at about 0400, Japanese news agency Kyodo said.
Apart from the Taepodong-2, the other missiles test-fired are thought to be shorter range.
Kyodo news agency said the first two were believed to be mid-range Rodong missiles, while Pentagon officials said they were Scud missiles.
The US and North Korea's neighbours had been on heightened alert in recent days amid suspicions that Pyongyang was preparing to launch the Taepodong-2 from the Musudan-ri launch site in the north-east of the country.
The Taepodong-2 has a range of up to 6,000 km (3,730 miles), putting parts of the US within striking distance.
'Strong protest'
The BBC's Charles Scanlon says North Korea has been feeling under pressure and ignored in recent months with the US refusing to negotiate on its demands over its nuclear plans.
This may be a way for North Korea to get attention and break the diplomatic log jam, our correspondent adds.
On Monday, Pyongyang warned it would launch an "annihilating" nuclear strike if its atomic facilities were pre-emptively attacked by the United States.
Washington dismissed the threat as "deeply hypothetical" and urged the North Koreans to return to six-party talks aimed at curbing the country's nuclear activities. The talks stalled last year.
North Korea had agreed with Japan to a moratorium on missile tests in 2002 and this was reaffirmed two years ago.
The last time North Korea tested a long-range missile was in 1998, when it launched a Taepodong-1 over northern Japan.
I echo Jerry's statement, and I add that it is time we do something to get this guy off his highhorse, and get North Korea out of the isolation they have been put through...
God Bless
Michelle!
Reviewed by Jerry Bolton (Reader)
Reviewed on July 4, 2006
And we are "talking" about it. Shame on us and you and them for letting that bastard get to this point in the first place.
Armageddon, a fact-based historical novel, is the third book of The First Strike Trilogy: A high-stakes race against time and politics unfolds in this gripping historical account of SIOP-62, revisit the tension of a pending nuclear attack, at a time
Mushroom Cloud, a fact-based historical novel, is the first book of The First Strike Trilogy: USA and the Soviet Union are building nuclear arms for a face off in a potential nuclear war in the late 1950's and early 1960's.
Armageddon, a fact-based historical novel, is the third book of The First Strike Trilogy: A high-stakes race against time and politics unfolds in this gripping historical account of SIOP-62, revisit the tension of a pending nuclear attack, at a time
God Bless
Michelle!