, TOKYO – Engineers and vehicles carrying liquid fuel have been seen gathering at North Korean bases housing missiles capable of striking most of Asia and parts of the United States, a Japanese newspaper says.

The reported activity at bases and other military sites in North Korea comes after media reports said last week the country might be preparing to test-fire a missile.

Citing Japanese and U.S. government sources, the Yomiuri Shimbun said increased activity had been seen at bases designed to launch Taepodong-2 missiles, which have with a range of between 3,500 km (2,175 miles) and 6,000 km, as well as Rodong missiles with a range of about 1,300 km.

Rodong missiles are capable of reaching any part of Japan, the paper said. North Korea test-fired a missile over Japan in 1998.

North Korea has called recent reports of launch preparations “speculation”, while South Korea's Foreign Minister, Ban Ki-Moon, said in an interview the suspicious ground movements could reflect maintenance of missile sites rather than preparations for a test.

The latest information on North Korean military movements came from Japanese EP-3 electronic surveillance aircraft as well as U.S. and Japanese reconnaissance satellites and monitoring of wireless communications, the paper said.

The paper said vehicles carrying liquid fuel were seen gathering at the bases, along with military personnel and engineers.

It was not clear whether the missiles were actually present at the launch bases, or whether the launch pads were in use, the paper quoted its sources as saying. North Korea had not deployed military vessels to monitor the sea near landing areas or recover fired missiles.

“The chances of an actual Rodong missile launch are slim,” the Yomiuri quoted an unidentified government official as saying. “We can't rule out the possibility that the activity was just a large-scale military drill.”

North Korean army, navy and air force units also appeared to be involved and their movements were observed across the country. Last week's reports said activity was observed mainly in the country's east.

The Defence Agency heightened its alert level and stepped up information gathering and surveillance, the Yomiuri said.

North Korea is thought to have one or two nuclear devices and experts believe it has deployed as many as 200 Rodong missiles.

China, Japan, Russia, South Korea and the United States are trying to persuade the North to ditch its suspected nuclear programmes in exchange for security guarantees and energy aid.