North Korea has moved three stages of a long-range rocket into position for a controversial launch in defiance of international warnings against violating a ban on missile activity.

Foreign news agencies were allowed a first-hand look at preparations under way at the coastal Sohae satellite station in north-western North Korea.

North Korea announced plans last month to launch an observation satellite during mid-April celebrations of the 100th anniversary of the birth of its founder Kim Il-sung. The US, Japan, Britain and other nations have urged North Korea to cancel the launch, warning that firing the long-range rocket would violate UN resolutions and Pyongyang's promise to refrain from engaging in nuclear and missile activity.

North Korea say that the launch is intended to improve the nation's faltering economy by providing detailed surveys of the countryside.

"Our country has the right and also the obligation to develop satellites and launching vehicles," Jang Myong Jin, general manager of the launch facility. "No matter what others say, we are doing this for peaceful purposes."

Experts say the Unha-3 rocket scheduled for liftoff between 12 and 16 April could also test long-range missile technology that might be used to strike the US and other targets.

North Korea has tested two atomic devices, but is not believed to have mastered the technology needed to mount a warhead on a long-range missile.

On Sunday, reporters were taken by train past desolate fields and farming hamlets to a new launch pad in Tongchang-ri in North Phyongan province, about 35 miles south of the border town of Sinuiju along North Korea's west coast.

All three stages of the 91-tonne rocket, emblazoned with the North Korean flag and "Unha-3", were visibly in position at the towering launch pad, and fuelling will begin soon, Jang said.

He said preparations were on track for liftoff and that international space, aviation and maritime authorities had been advised of the plan, but did not provide exact details on the timing of the fuelling or the mounting of the satellite.

Engineers gave reporters a peek at the 100kg Kwangmyŏngsŏng-3 satellite due to be mounted on the rocket, as well as a tour of the command centre.

About two weeks before North Korea unveiled its rocket plan, Washington announced an agreement with Pyongyang to provide it with much-needed food aid in exchange for a freeze on nuclear activity, including a moratorium on long-range missile tests. The food aid plans, as well as a recently revived project to conduct joint searches for the remains of US military personnel killed during the Korean war, have now been suspended.

Jang denied the launch was a cover for a missile test, saying the relatively diminutive rocket and fixed Sohae station would be useless for sending a mobile intercontinental ballistic missile.

"During the recent senior-level North Korea-US talks, our side made clear there's only a moratorium on long-range missile launches, not on satellite launches," he said. "The US was well aware of this."

Japan and South Korea, meanwhile, said they are prepared to shoot down any parts of the rocket that threaten to fall in their territory – a move North Korea's foreign ministry warned would be considered a declaration of war.

The launch is scheduled to take place three years after North Korea's last announced attempt to send a satellite into space, a liftoff condemned by the UN security council. North Korea walked away from nuclear disarmament negotiations in protest, and conducted an atomic test weeks later that drew tightened UN sanctions.