SEOUL, South Korea -- North Korea has fired a missile into the Sea of Japan, escalating a tense standoff on the peninsula as world leaders gather in Seoul for the inauguration of South Korea's new president.

In a provocative move ahead of Roh Moo-hyun's inauguration, Pyongyang fired a missile into the sea between the Korean Peninsula and Japan, South Korea's Ministry of Defense said, rattling markets around the region.

The land-to-ship missile was fired on Monday, as U.S. Secretary of State Colin Powell, Japanese Prime Minister Junichiro Koizumi and other dignitaries arrived in Seoul for Tuesday's swearing-in ceremony of the untested 56-year-old leader.

Tensions between Washington and North Korea have heated up in recent months after the United States said Pyongyang admitted in October it was working on a secret nuclear program -- something the North has denied.

North Korea has responded by kicking out international inspectors and intensifying its rhetoric against Washington.

The missile was fired from the northeastern coast of North Korea and traveled about 60 kilometers (37 miles) before plunging into the Sea of Japan.

South Korea's defense department would not release any other details about the missile but the incident is being investigated.

A North Korean official attending the Non-Aligned Movement summit in Malaysia told Reuters Tuesday the missile test had been undertaken for "security" reasons, but would not elaborate.

In Washington, the White House said preliminary reports showed it was a short-range missile.

Some reports suggest the missile was a Chinese-made Silkworm missile, which has a range of around 80 kilometers, but this information has not been confirmed.

In August 1998, North Korea fired a multistage missile that flew over Japan and landed in the Pacific Ocean, proving the Koreans can strike any part of Japan's territory.

The main islands of Japan are about 1,000 kilometers (600 miles) from where the latest missile was launched, beleived to be the Hamgyong province.

Newspaper reports in South Korea say the North Korean army is currently undertaking (northern) winter exercises and the firing could have been part of that activity.

North Korean soldiers at the border with the South

"We believe that this is part of North Korea's usual tests of its weapons during the military exercise," Col. Kim Sung-ok, an officer at South Korea's Joint Chiefs of Staff, told Associated Press.

However, the timing is not regarded as purely coincidental and may be related to the ongoing tension between the United States and North Korea over Pyongyang's revived nuclear program.

In another suspected provocative move late last week, a North Korean MiG-19 jet flew into South Korean airspace over the Yellow Sea near Yongpyong Island. (Jet move 'provocative')

The North may also be attempting to overshadow President Roh's inauguration.

Last year's Soccer World Cup celebrations were marred by a deadly naval clash between North and South.

In Washington, a White House official said that, assuming the early reports are accurate, the missile was not threatening because it had limited capabilities.

The official said initial U.S. assessments were that North Korea was "being mischievous" on the eve of Roh's inauguration.

"We believe this is one of their short-range tactical missiles," the U.S. official said. "We are looking into it for more information but that is what it appears to be."

A Japanese Foreign Ministry official told CNN the government was still analyzing incident, but if it was a short-range missile then it was not in breach of a recent agreement.

In 2001, North Korea imposed a voluntary moratorium on ballistic missile testing through 2003.

--Senior White House Correspondent John King and Correspondent Rebecca MacKinnon contributed to this report.