Planned high-level talks between North and South Korea -- the first for six years -- were called off at the last minute Tuesday, because of a dispute over the status of their respective chief delegates.

The rift over a matter of protocol was a stark example of the trust deficit that still dominates relations 60 years after the end of the Korean War.

South Korean police said Friday they would stop a planned launch of anti-North Korean leaflets across the tense border, after Pyongyang threatened to retaliate.

A group of defectors from the North had said they would float 200,000 leaflets over the heavily militarized frontier by balloon on Saturday to protest Pyongyang's dire human rights record.

North Korea vowed Sunday to strengthen its nuclear weapons, a day after announcing it is in a "state of war" with South Korea, and said it would never trade its atomic deterrent for aid.

Tensions have risen sharply since the United Nations tightened sanctions in response to the North's nuclear and missile tests, and since the United States and South Korea launched military drills south of the border.

Tens of thousands of North Korean soldiers and civilians held a huge rally and march in Pyongyang on Friday, in a mass display of support for a possible military strike against the United States.

The rally in Pyongyang's giant Kim Il-Sung square was attended by soldiers, veterans, workers and students, all wearing military uniforms. The North's young leader, Kim Jong-Un, was not present.

North Korea can never be made to abandon its nuclear weapons program, South Korean President Lee Myung-Bak said Friday, arguing that only regime collapse could remove the threat from Pyongyang.

As the U.N. Security Council continues to debate how to punish the North for its latest nuclear test, the outgoing president suggested the best way forward was to try to foment unrest among the North Korean people.

More than 100,000 troops and civilians staged a mass rally in Pyongyang to celebrate North Korea's nuclear test and praise the "matchless" bravery of leader Kim Jong-Un, state media said Friday.

The rally in the capital's sprawling Kim Il-Sung square on Thursday was attended by top party and military officials, as well as police workers and students, the official Korean Central News Agency (KCNA) said.

Israel on Tuesday condemned North Korea's latest nuclear test, saying the world must send "a clear message" to Pyongyang that such activities were unacceptable, a foreign ministry spokesman said.

"Israel strongly condemns North Korea's nuclear test, and joins the international community in expressing the grave danger that this act poses to regional stability and international peace and security," Yigal Palmor said in a statement.

North Korea Saturday condemned a recent visit by the South's President Lee Myung-Bak to an island close to their disputed border and reiterated that it only recognises a demarcation line drawn by Pyongyang.

A National Defence Commission spokesman said Lee's trip Thursday to Yeonpyeong island, shelled by the North in 2010, intended to raise tensions and rally support for the conservative ruling party ahead of December elections.

South Korea, the United States and Japan will hold high-level talks in Seoul next week about developments in North Korea following its failed long-range rocket launch, a report said Thursday.

Lim Sung-Nam, South Korea's chief nuclear envoy, his Japanese counterpart Shinsuke Sugiyama and the U.S. special envoy on the North Glyn Davies will meet on Monday, Yonhap news agency quoted a foreign ministry official as saying.

New satellite images show more work under way at North Korea's nuclear test site, but give no indication of when a test may occur, a U.S.-based specialist website reported Saturday.

There is widespread speculation that the North may carry out another atomic weapons test -- its third -- following international criticism of a failed rocket launch on April 13.