North Korea has vowed to launch satellites "one after another", vigorously rejecting international condemnation of an April 13 launch that was seen overseas as a disguised ballistic missile test.

The rocket, which Pyongyang said was intended to put a satellite into orbit, disintegrated some two minutes after blast-off. The UN Security Council strongly condemned the launch and said it would tighten existing sanctions.

In a statement late Thursday, the North said it has already completed an investigation into the cause of the failure. The data and experience gained would be "a reliable guarantee for greater success in the days ahead", it said.

"No matter how loudly the US and Japanese reactionaries and their followers may cry and no matter how frantically the Lee Myung-Bak group of rats may squeak, the DPRK's (North Korea's) satellites for peaceful purposes will be put into space one after another."

The North has criticised South Korea's conservative President Lee in extreme terms in recent months.

The statement, from a spokesman for the Korean Committee for Space Technology, also referred to him as a "rabid dog", an "underwit", an "ignorant president" and "human scum".

The North insists its satellite launch was not banned under UN resolutions and did not breach a deal with the United States announced in February.

Under that agreement, the North agreed to suspend an uranium enrichment programme and impose a moratorium on nuclear and long-range missile tests, in return for 240,000 tonnes of food aid.

Washington has suspended delivery of the food and Pyongyang has threatened unspecified retaliation for what it called a hostile US stance.

Several analysts believe it will conduct a third nuclear weapons test, following tests in 2006 and 2009 that also followed rocket launches.

The statement described the value of the US food aid as "petty" and again insisted it was the victim of double standards.

It said the United States and other nations had never sought prior approval for satellite launches that used carrier rockets.

"Did the US or Japan lift their satellites with puffs of breath or with magic strength?"

The rocket launch was to have been a centrepiece of celebrations for the 100th anniversary on April 15 of the birth of founding president Kim Il-Sung.

The North Thursday demanded that South Korea apologise for alleged insults during the festivities, or face a "sacred war".