"There was no sign of North Korea firing a missile today," said a spokesman for the Joint Chiefs of Staff (JCS), dismissing unconfirmed reports from Tokyo.

"This information is shared by both South Korea and the United States."

On Monday North Korea test-fired a short-range anti-ship missile into the Sea of Japan (East Sea) for the third time this year as part of routine military exercises, according to the JCS.

The unconfirmed report of a fourth test Tuesday came for Japan Broadcasting Corp (NHK) on its midday bulletin which referred to unspecified "information" about a new missile test.

An official from the Japan Defense Agency said the government was investigating the report.

In April Japan was forced to retract an announcement by its defence agency that North Korea had test-fired a missile.

The embarrassed defense agency said it had made a mistake but declined to explain how it happened.

North Korea test-fired short-range anti-ship missiles on February 24 and March 10 prior to its latest test on Monday.

North Korea's development of missiles, particularly long-range ballistic ones, has sparked concern for years in Japan and the United States.

The impoverished Stalinist state is known to have deployed short-range Soviet-developed Scud missiles while developing longer-range ballistic missiles codenamed Rodong and Taepodong.

Pyongyang alarmed Tokyo in August 1998 by test-launching a Taepodong-1 missile over Japan with a range of up to 2,000 kilometers (1,240 miles), claiming it was a satellite launch.

Washington is worried that the Stalinist state could deploy ballistic missiles capable of hitting US territory.

SPACE.WIRE