By Richard Spencer in Beijing
The missile, known as a Musudan-type, was shown to the public at a vast military parade in the North Korean capital Pyongyang, according to the reports.
South Korean and American intelligence reports suggest it was then tested not from North Korean soil but from Iran, with which North Korea is known to have close military co-operation.
The missile, which could target the US military on the Pacific island of Guam, was previously unrecorded.
North Korea has a known capacity in short and medium-range missiles, including the Taeopodong-1 which it fired over Japan in 1998 to the alarm of Tokyo and its allies in Washington.
However, it has had less success developing long-range missiles.
It has been working for several years on a Taepodong-2, which would be targeted at the western seaboard of the United States.
But a test last July failed, landing in the sea not far from the North Korean and Russian border.
The new missile is said have been identified by American military satellite pictures of the April rally to commemorate the 75th anniversary of the founding of the North Korean army, and to be based on Soviet technology.
The Japanese defence ministry said that the new missile might be able to travel 3,000 miles at middle altitude.
“We acknowledge that such a new type of missile is being developed by North Korea in addition to the existing missiles,” an official said.
Yonhap, the South Korean news agency, quoted a source in Washington as saying: “We did obtain intelligence tips that the missile was test-fired in Iran. I understand that the intelligence communities of relevant countries are tracking down the information.”
The Iran connection could well be a favour in return for North Korea agreeing to share the results of its nuclear test last October with Teheran.
The countries were both beneficiaries of the nuclear know-how network created by the Pakistani scientist AQ Khan, and have been known previously to co-operate on missile technology.
