South Korea accused North Korea Monday of "deceptive" appeals for dialogue and said Pyongyang was determined to keep its nuclear weapons despite international efforts to revive disarmament talks.

Unification Minister Hyun In-Taek, in a strongly worded speech at the start of a week of nuclear diplomacy, also accused Pyongyang of exaggerating food shortages for political reasons.

Four retired state leaders including former US president Jimmy Carter are to visit the communist state this week for discussions on reducing inter-Korean tensions, denuclearisation and food shortages.

China's nuclear envoy Wu Dawei is due in Seoul Tuesday for talks on reviving long-stalled six-party talks on the North's nuclear disarmament.

Inter-Korean relations have been icy since Seoul accused Pyongyang of torpedoing a warship in March 2010 with the loss of 46 lives.

The North denies the charge but shelled a South Korean border island last November, killing four people including civilians. In a change of tack this year, it has been appealing for dialogue.

Hyun, in a speech to European business leaders, blamed the North's "intransigence" for the uncertainty in relations, saying it had refused to utter a word of apology for the attacks or commit to denuclearisation.

The minister, who handles cross-border affairs, said the recent overtures "appeared to be a classic case of North Korea's deceptive 'peace offensive'", which he termed a worn-out tactic.

He described the North's third-generation hereditary succession process involving leader Kim Jong-Il and his youngest son Jong-Un as "a somewhat bizarre experiment in modern history".

He said it was impossible to predict whether the eventual transition would succeed. But the North's political, economic and social circumstances were much more unstable than in the early 1990s, when Kim Jong-Il inherited power from his own father.

There seemed "nearly no hope" for the North's state-directed economy, Hyun said.

But despite unprecedented appeals for international food aid, Hyun said the North's food shortage was not particularly worse this year and there appeared to be some political motivation for the pleas.

Some Seoul officials say the North is trying to stockpile food before a major anniversary next year marking 100 years since the birth of late founding leader Kim Il-Sung.

Carter, speaking in Beijing, said however he would be looking at ways to ease sanctions on Pyongyang that he said had worsened the food crisis.

"It is a horrible situation there and we hope to induce other countries to help alleviate (the crisis), including South Korea, which has cut off all supplies of food materials to North Koreans," Carter told journalists.

"When there are sanctions against an entire people, the people suffer the most and the leaders suffer the least."

Carter and his group also said they want to focus on denuclearisation. China is trying to restart the six-nation nuclear talks which it hosts and which also group the two Koreas, the United States, Russia and Japan.

But Hyun said Pyongyang's reaction to developments in Libya "only revealed that North Korea is determined not to denuclearise itself".

Pyongyang has condemned air strikes by the US-led coalition on Libya, and said they resulted from that country's decision to give up its nuclear weapons.

Hyun said the other five parties agree there should be inter-Korean talks, and then US-North Korean dialogue before the full talks resume.

But inter-Korean dialogue should not be a brief stopover en route to the six-party talks, he said.

"For us to move forward, North Korea must show a responsible attitude on last year's two brutal provocations. Only then will we be able to enter a new chapter in inter-Korean relations."