Japanese officials said that North Korea test-fired an anti-ship missile off its west coast Tuesday in an apparent response to Tokyo's launching of spy satellites days earlier.

But South Korean officials, who initially called the reported launch "routine," later said there was no evidence it had occurred. Then a Japanese official said the test-fire had not been confirmed.

"We have information about the missile but we have no confirmation," Chief Cabinet Secretary Yasuo Fukuda told reporters.

Japanese officials have refused to disclose where they received the information, saying they were linked to security secrets.

A Defense Agency official also backtracked from an earlier announcement by the Japanese navy's top official that North Korea had fired a short-range missile. The agency only had information about a launch, and no confirmation, he said on condition of anonymity.

Japanese officials said North Korea fired a missile from the peninsula's northwest coast into the Yellow Sea, although they said it posed no immediate security threat.

In Washington, a Pentagon official also confirmed the launch and said the United States does not view it as a threat.

"Since this is not a ballistic missile, we do not think that this would pose a direct threat to the security of Japan," Japanese Foreign Ministry spokesman Hatsuhisa Takashima said.

Japan's launch of spy satellites Friday to monitor North Korea's suspected nuclear weapons program had angered Pyongyang, which threatened to test-fire a missile. Tuesday's reported launch added to growing fears in Japan that the reclusive communist state might take advantage of the war in Iraq to escalate its missile and nuclear development.

Koichi Furusho, chief of staff of South Korea's Maritime Self-Defense Forces, said Tuesday's reported test-fire was likely a routine test. He played down the possible dangers and told reporters that his forces were not placed on any special alert.

But South Korea's Defense Ministry later said there was no evidence that North Korea had test-fired a missile.

"South Korean and U.S. military intelligence officials have checked on the report and concluded that there was no missile launch by North Korea," a ministry official said on condition of anonymity.

South Korea's new government, headed by President Roh Moo-hyun, has made strong efforts to reduce tensions with North Korea.

The U.S. military announced Tuesday that U.S. stealth fighter jets and other aircraft and troops currently in South Korea for joint war games will remain after the exercises are finished to act as a deterrent against North Korea.

In 1998, North Korea fired a long-range missile that flew over Japan and plunged into the Pacific Ocean. It is believed to possess missiles that could reach parts of the United States.

North Korea test-fired two short-range missiles in late February and early March amid tensions over its suspected nuclear weapons programs. Washington and South Korea have criticized the tests as attempts to force the United States into direct talks.

The Korean nuclear crisis flared last October, when U.S. officials said North Korea admitted having a nuclear program in violation of a 1994 agreement.