North Korea said Friday it would launch a long-range rocket next month to put a satellite into orbit, a move that would breach a United Nations ban imposed after previous launches.

The announcement came just 16 days after the North's new leaders agreed to suspend long-range missile tests as part of a deal under which it would receive 240,000 tonnes of US food aid.

Blast-off will be between April 12 and 16 to mark the 100th anniversary of the birth of founding leader Kim Il-Sung, the communist state's official news agency and state television said.

Its last long-range rocket launch on April 5, 2009, purportedly to put a satellite into orbit, brought UN Security Council condemnation and a tightening of sanctions.

Pyongyang quit six-party nuclear disarmament talks in protest at the censure and conducted its second atomic weapons test the following month.

The surprise deal to suspend long-range missile tests, under which Pyongyang also promised to freeze its uranium enrichment plant, had raised hopes of eased tensions. But one analyst said Friday's announcement effectively killed it off.

The North says its satellite launches are for peaceful purposes while the United States and other nations call them disguised missile tests.

UN Security Council Resolution 1874, passed after the North's second nuclear test, demands that it "not conduct any further nuclear test or any launch using ballistic missile technology".

South Korea's foreign ministry, in a strongly worded statement, said any launch would breach the resolution and be a "grave, provocative act".

Japan, whose airspace was breached by the 2009 rocket, also said a launch would violate UN resolutions. It said it would "strongly demand self-restraint" by the North.

A Unha-3 rocket will launch a home-built polar-orbiting earth observation satellite known as Kwangmyongsong-3, a spokesman for the Korean Committee for Space Technology said in a statement.

Repeating its arguments of 2009, the North said such satellites are indispensable for economic development and in line with the peaceful use of space.

The launch "will greatly encourage the army and people... in the building of a thriving nation", it added.

"A safe flight orbit has been chosen so that carrier rocket debris to be generated during the flight would not have any impact on neighbouring countries," it said, promising to abide by international regulations.

The North said the rocket would be launched southward from the Sohae Satellite Launching Station in Cholsan county on its northwest coast.

It has been developing a new launch site at Tongchang-ri in the county and this would be the first launch there.

The Unha-3 is known outside the North as the Taepodong-3 and is theoretically capable of reaching US territory, said Baek Seung-Joo of the Korea Institute for Defence Analyses.

"Following the alleged satellite launch attempt in 2009, this is another ploy to heap pressure on the United States by conducting a test-launch of a rocket which can easily be converted to weapons use," said Yang Moo-Jin of Seoul's University of North Korean Studies.

"It also wants to show off to the world it has become a strong state with technological and military prowess as it enters a new era under Jong-Un and marks the 100th anniversary of Kim Il-Sung," Yang told AFP.

Kim Jong-Un is Kim Il-Sung's grandson. He took over the leadership after his own father Kim Jong-Il died on December 17.

Kim Yong-Hyun, of Seoul's Dongguk University, said the North would insist its launch was for peaceful scientific purposes and unrelated to the missile test moratorium.

"The US will, of course, make a strong response, regarding it as a long-range missile launch," he told AFP, adding it was unclear whether it would derail negotiations.

But Daniel Pinkston, Seoul-based analyst with the International Crisis Group, said the announcement means the February 29 agreement with the United States "is pretty much dead".

Such rockets, he told AFP, are "inherently dual-use technology: if you can launch a satellite you can deliver a warhead at long range".

Paik Hak-Soon of the Sejong Institute think-tank said the move "throws a wrench" into US efforts to stop the North coming to the fore in an election year.

The launch will also come just after South Korea's April 11 general election. The North is bitterly hostile to the ruling conservative party, which scrapped the aid and engagement policy of previous liberal governments.