SEOUL/TOKYO: International pressure grew on North Korea to call off a planned rocket launch, seen by some governments as another missile test, while Japan put its military on alert to shoot down any rocket that threatens its territory.

North Korea notified United Nations agencies on Tuesday of its plan to launch what it called an "earth observation satellite" some time between Feb. 8 and 25.

Pyongyang has said it has a sovereign right to pursue a space programme, although the United States and other governments suspect such rocket launches are tests of its missiles.

Japan's defence minister, Gen Nakatani, told a media briefing on Wednesday he had issued an order to shoot down any "ballistic missile threat".

Tension rose in East Asia last month after North Korea's fourth nuclear test, this time of what it said was a hydrogen bomb.

A rocket launch coming so soon after would raise concern that North Korea plans to fit nuclear warheads on its missiles, giving it the capability to launch a strike against South Korea, Japan and possibly targets as far away as the US West Coast.

North Korea last launched a long-range rocket in December 2012, sending an object it described as a communications satellite into orbit.

South Korea warned the North it would pay a "severe price" if it goes ahead with the launch.

"North Korea's notice of the plan to launch a long-range missile, coming at a time when there is a discussion for (UN) Security Council sanctions on its fourth nuclear test, is a direct challenge to the international community," the presidential Blue House said in a statement.

Russia's Foreign Ministry said Pyongyang was demonstrating "an outrageous disregard for the universally recognised norms of international law," while France said the launch would merit a firm response from the international community.

UN Secretary-General Ban Ki-moon urged North Korea not to use ballistic missile technology, which is banned by Security Council resolutions.

'EXTREMELY CONCERNED'

China, under U.S. pressure to use its influence to rein in the isolated North, said Pyongyang's right to space exploration was restricted under U.N. resolutions.

China is North Korea's sole main ally, though Beijing disapproves of its nuclear programme.

"We are extremely concerned about this," Chinese Foreign Ministry spokesman Lu Kang told a briefing on Wednesday.

"In the present situation, we hope North Korea exercises restraint on the issue of launching satellites, acts cautiously and does not take any escalatory steps that may further raise tensions on the Korean peninsula."

Reports of the planned launch also drew fresh US calls for tougher UN sanctions that are already under discussion in response to North Korea's Jan. 6 nuclear test.

A spokeswoman for the International Maritime Organization, a UN agency, said it had been told by North Korea of the plan to launch a satellite.

The Washington-based North Korean monitoring project 38 North said commercial satellite images of North Korea's Sohae launch site taken on Monday showed activity consistent with preparations for a launch within North Korea's given timeframe, but no indications that this was imminent.

North Korea said the launch would be conducted in the morning one day during the announced period, and gave the coordinates for the locations where the rocket boosters and the cover for the payload would drop.

Those locations are expected to be in the Yellow Sea off the Korean Peninsula's west coast and in the Pacific Ocean to the east of the Philippines, Pyongyang said.

South Korea told commercial airliners to avoid flying in areas of the rocket's possible flight path during the period.