North Korea appears to have moved a medium range missile to its east coast, South Korean Defence Minister Kim Kwan-Jin said Thursday, prompting fears of a strike against South Korea or Japan.

Addressing a parliamentary defence committee meeting, Kim rejected some media reports that it might be a longer-range missile unveiled last year, saying it looked like an intermediate-range Musudan.

Kim said it could not be confirmed if the missile was armed with a warhead.

"It could be aimed at test firing or military drills," he told the lawmakers. The Musudan missile was first unveiled at a military parade in October 2010 and is believed to have an intended range of around 3,000 kilometres (1,860 miles).

That would cover anywhere in South Korea or Japan, but fall short of US military bases in Guam.

The Musudan is not known to have been tested, so its capacity and accuracy is unproven even over a medium range.

Yonhap news agency cited South Korean intelligence sources as saying the North might launch the missile on April 15, the birth anniversary of founding leader Kim Il-Sung.

The United States said Wednesday it was sending ground-based missile interceptors to Guam in response to North Korean threats to strike the Pacific island and other US targets.

A US territory that is home to 6,000 American military personnel, submarines and bombers, Guam lies 3,380 kilometres southeast of North Korea.