New satellite imagery shows advanced preparations by North Korea for its rocket launch, including a mobile radar trailer and apparently empty fuel tanks, a US website reported Monday.

The North says its rocket will put a peaceful satellite into orbit between April 12-16, while the United States and its allies accuse Pyongyang of planning a ballistic missile test banned under UN resolutions.

The photography "reveals that North Korea has undertaken more extensive preparations for its planned April rocket launch than previously understood", the 38 North website (38north.org) reported.

It said a March 28 photo of the entire site at Tongchang-ri in the country's far northwest appeared to show a trailer with a dish antenna -- probably a radar tracking system -- atop a ridge at the end of a new dirt road.

The image taken by US firm DigitalGlobe also shows previously empty, fenced-in areas which are filled with rows of what are probably empty fuel and oxidiser tanks, said the website, which carried some of the imagery.

38 North said the tanks were apparently dumped after their contents were transferred to buildings that will directly fuel the rocket's first stage.

"The large number of apparently empty tanks indicates that the transfer process may have been close to completion," said the website, a project of the US-Korea Institute at the Johns Hopkins School of Advanced International Studies.

There also appeared to be activity near the horizontal launcher assembly building where press reports indicated the stages of the Unha-3 rocket are located.

Last Friday 38 North published a series of other satellite images from DigitalGlobe, showing work on schedule for the widely condemned launch.

ASEAN voices 'real concern' on N. Korea rocket launch
Phnom Penh (AFP) April 2, 2012 - Southeast Asian nations voiced "real concern" on Monday about North Korea's planned rocket launch, which the United States and its allies describe as a ballistic missile test.

"There is a real concern on the development in the Korean peninsula," said ASEAN chief Surin Pitsuwan after foreign ministers of the 10-member Association of Southeast Asian (ASEAN) met in the Cambodian capital.

"Instability up there could lead to diminishing confidence in the region as a whole."

Philippine Foreign Secretary Albert del Rosario called the launch "unacceptable" and in violation of United Nations resolutions, and said he expected ASEAN members to support his country's position.

ASEAN leaders are due to hold a two-day summit in Phnom Penh from Tuesday, and while North Korea is not a member of the block the launch is expected to feature in their discussions.

Asked whether ASEAN agreed with Manila that the launch was unacceptable, Surin said: "ASEAN has expressed very, very serious concern but in what language it will come out, I don't know. We have to wait and see."

Del Rosario told AFP after the meeting he was "very happy" with how the discussion on the launch had gone with his regional counterparts.

"I think the countries that spoke on the topic of the DPRK (North Korea) launch were all of the opinion that we should be discouraging DPRK from undertaking that launch," he said.

Manila announced on Sunday it had lodged diplomatic protests with Pyongyang representatives at the United Nations, in China, and in ASEAN nations.

Indonesian Foreign Minister Marty Natalegawa told reporters he had also "communicated our concern about the developments on the Korean peninsula".

Pyongyang announced last month it would fire a rocket between April 12-16 to place a satellite in orbit, sparking alarm in the region.

A US diplomat has said debris from the launch are expected to land off the coast of key US regional ally the Philippines, an archipelago made up of thousands of islands.

The United States and other nations say the planned launch is a disguised ballistic missile test, and would breach a UN ban on North Korean missile launches.