North Korea has fired a short-range missile into the Yellow sea, media reports said Tuesday.

Japanese public broadcaster NHK quoted unidentified officials as saying Tokyo was trying to verify the details of a report received Tuesday from a third country that the communist nation had fired a missile. NHK said the latest firing did not involve a ballistic missile.

South Korea's Yonhap news agency said two missiles were fired on Monday, citing an unidentified defense official. Japanese daily Mainichi also carried a similar report, calling the test a routine military exercise.

NHK did not say who provided the information, which the report said Japan has yet to confirm independently.

In Washington, the Pentagon declined to confirm or deny whether any missile shot had been detected.

"We cannot provide information regarding specific intelligence," said Marine Maj. Stewart Upton, a Defense Department spokesman. "However, our concerns about missile activities in North Korea are long-standing and well documented."

Japan's foreign ministry and defense officials said they could not confirm the report.

The communist nation frequently test-fires short-range missiles, including two in March. It has been under a self-imposed moratorium on long-range missile tests since 1999, though a U.S. official has said that earlier this year the country tested the engine of a long-range missile that could reach the American West coast.

Tuesday's reports come amid heightened tensions on the peninsula. The North stopped disabling its nuclear facilities in August, around the same time reports say autocratic North Korean leader Kim Jong Il suffered a stroke. North Korea denies Kim, 66, is ill.

In 2006, North Korea conducted an underground nuclear test, and a previous missile test showed it also had the means to deliver one. But it is currently barred by U.N. sanctions from testing ballistic missiles and components.

"North Korea's development, deployment and proliferation of missiles and missile-related materials, equipment and technology pose a threat to the region and the world," Upton said.

Japan imposed tight trade sanctions against the impoverished communist nation in 2006 after North Korea tested ballistic missiles in the waters between the two countries and conducted a test explosion of a nuclear device.