North Korea vowed on Sunday to push ahead with what it says are peaceful nuclear and space programmes, rubbishing calls from the five permanent UN Security Council members.

The communist North condemned a statement issued Thursday by the United States, ally China, Russia, France and Britain on the sidelines of a non-proliferation meeting in Vienna.

They had expressed "serious concern" and urged Pyongyang to "refrain from further actions which may cause grave security concerns in the region, including any nuclear tests".

There has been widespread speculation the North could stage its third nuclear test following a failed rocket launch on April 13 that sparked international criticism.

A South Korean nuclear expert had said that the North has finished preparations for a third nuclear test, while satellite photos of the North's Punggye-ri test site show work in progress.

Thursday's statement was an "illegal act that infringes upon" the North's right to use space and nuclear power for peaceful purposes, an unnamed North Korean foreign ministry spokesman said through state media.

"We will... persistently safeguard the sovereignty of our nation, based on self-defensive nuclear deterrent, and strongly pursue our peaceful space development and the development of our nuclear power industry," the spokesman said.

US Secretary of State Hillary Clinton said Friday in Beijing that Washington was ready to work with Pyongyang if it changed course, but she voiced doubts about the regime's intentions.

Seoul welcomes North Korean sanctions
Seoul (UPI) May 4, 2012 - It may be only three North Korean businesses but Seoul welcomed U.N. sanctions against firms believed involved in Pyongyang's failed rocket launch last month.

"Although the number of North Korean firms added to the U.N. sanctions was (only) three, they are core organizations continuously leading transactions in connections with weapons of mass destruction," South Korean Foreign Ministry spokeswoman Han Hye-jin said.

"Rather than the number, our main concern is how to proceed with an implementation of the additional sanctions," Han said.

North Korea has been under U.N. sanctions for previous nuclear and missile tests in 2006 and 2009, a report by South Korea's Yonhap news agency said.

The latest attempt to sanction North Korean firms focused on 40 businesses proposed by South Korea, the United States, Japan and the European Union, Yonhap said.

Only three eventually were sanctioned by the U.N. Security Council because of objections by China, one of the 15 nations on the council, Yonhap said. Council members with veto powers are China, France, Russia, the United Kingdom and the United States.

The three firms are Green Pine Conglomerate, Amroggang Development Banking Corp. and Korea Heungjin Trading Co.

The businesses are banned from international trading and likely will have their international assets frozen.

The companies are believed connected to development of technology for the launch on April 13 of what Pyongyang had said was to put an Earth-observation satellite into orbit.

But the satellite called Kwangmyongsong-3, atop a long-range rocket, failed to enter orbit because the rocket disintegrated several minutes after takeoff.

North Korean state media said little about the failure of the launch, which was to mark the 100th birthday on April 15 of the late Kim Il Sung, founder of North Korea and grandfather of Kim Jong Un, 28, and the new leader of North Korea.

Western governments strongly objected to the launch, which they suspected was to test long-range missile technology that could carry nuclear weapons.

Despite censuring North Korea, the Security Council, including China, also said it remained firmly behind resumption of the six-party talks as soon as possible.

The six-party disarmament talks, involving the two Koreas, the United States, Japan, Russia and China, have been stalled since 2008.

A resumption of the talks has waxed and waned since 2008, with the Security Council -- backed by China -- consistently urging all parties to get back to the negotiating table to avoid tensions on the Korean Peninsula reaching a military confrontation.

A report in China's state-run news agency Xinhua several days after North Korea's failed rocket launch last month said Beijing is keen to see the resumption of talks.

"The six-party talks are the only efficient platform for the parties concerned to sit down and discuss these issues," the Xinhua report said.

"The process to restart the talks should not be delayed, and the relevant parties should do their utmost to ensure the talks resume as soon as possible."

Last week Seoul accused North Korea of sending jamming signals that affected Global Positioning System navigation on dozens of airline flights over South Korea.