"North Korea conducted a missile firing drill today as part of its annual military training," JCS spokesman Kim Hyoung-Kyu said.

He did not say exactly when and where the surface-to-ship missile was launched.

Kim downplayed the test, saying it was part of North Korea's "routine" military exercises which were closely monitored in South Korea.

"We have witnessed such tests three times this year," he said.

An unidentified South Korean defense official told Yonhap new agency that the missile firing was presumed to be part of tests to improve the function of North Korea's surface-to-ship missiles.

"The South Korean and US intelligence authorities are analyzing the missile firing under ... close cooperation," the official was quoted as saying.

North Korea test-fired short-range anti-ship missiles on February 24 and March 10 this year off its east coast into the Sea of Japan (East Sea).

A report that North Korea had test-fired a missile on April 1 was denied by South Korea's defense ministry.

Officials accompanying Japanese Prime Minister Junichiro Koizumi to the Asia Pacific Economic Cooperation (APEC) summit that started in Bangkok Monday said they were trying to confirm the North's missile test.

"There is information that a missile was fired on the east coast (of North Korea) but it is unconfirmed," Koizumi's spokesman Jiro Okuyama said.

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 with concerns over its suspected possession of nuclear weapons doubling the security alarm.

The United States and North Korea have been locked in a standoff since last October on Pyongyang's nuclear weapons ambitions, after a senior US official accused the state of breaching a 1994 anti-nuclear pact by pursuing a nuclear development program.

Separately, North Korea's official Korean Central News Agency repeated that the Stalinist state, faced with US hostility, had no choice but to build up its nuclear weapons stockpile and that North Korea stood ready to display its nuclear deterrent.

"Our republic will further strengthen nuclear deterrence force in a situation in which the United States, without dropping its hostile policy toward the DPRK, continues to seek nuclear confrontation," it said.

It added that Pyongyang was ready to display its nuclear capability "when an appropriate time comes."

US President George W. Bush said for the first time Sunday that he would explore ways of satisfying North Korea's demand for an assurance that the United States would not invade the Stalinist state, but ruled out a bilateral non-aggression accord.

The Stalinist state blames Washington for the year-long nuclear crisis and says it will not disarm -- North Korea's term for scrapping its atomic weapons -- until the United States commits to a legally binding non-aggression pact.

SPACE.WIRE