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.

A half dozen ominous new North Korean missiles showcased at a lavish military parade were clumsy fakes, analysts say, casting more doubt on the country's claims of military prowess after its recent rocket launch failure.

The weapons displayed April 15 appear to be a mishmash of liquid-fuel and solid-fuel components that could never fly together. Undulating casings on the missiles suggest the metal is too thin to withstand flight. Each missile was slightly different from the others, even though all were supposedly the same make. They don't even fit the launchers they were carried on.

Apparently new long-range ballistic missiles displayed at a North Korean military parade this month were mock-ups, according to two German experts who termed the exercise "a nice dog and pony show".

One of the missiles on show in Kim Il-Sung Square on April 15 -- transported on a launcher of apparent Chinese design -- seemed to be a new addition to the nuclear-armed country's long-range arsenal, according to analysts at the time.

North Korea's military Monday threatened "special actions" soon to turn parts of the South Korean capital to ashes, accusing Seoul's conservative government of defaming its leadership.

The North has for months been criticizing the South's President Lee Myung-Bak in extreme terms and threatening "sacred war" over perceived insults.

North Korea has warned of retaliation after the U.S. scrapped food aid over its rocket launch, raising fears of a new nuclear test, as China reportedly suspended a refugee deal with its wayward ally.

In a defiant statement late Tuesday, the nuclear-armed North broke off a bilateral agreement to halt testing of nuclear weapons and long-range missiles after Washington suspended much-needed food aid.

Disco group Boney M will join a candlelight rally in Seoul supporting North Korean refugees who fled to China and now face repatriation to their impoverished homeland, organizers said Tuesday.

Boney M, who was hugely popular during the disco era of the late 1970s, will join the rally outside the Chinese embassy, said concert promoter Btechnic in a statement.

The U.N. Security Council on Monday tightened sanctions on North Korea over its failed rocket launch and warned of new action if the isolated state stages a new nuclear test.

The 15-member council -- including the North's closest ally China and nuclear-armed Pakistan -- "strongly condemned" the launch in a statement which highlighted "grave security concerns" in Asia.

North Korea will push for the launch of a new and bigger rocket as part of a five-year space program despite last week's failed launch, a pro-North Korean newspaper in Japan said Monday.

The North last week carried out a rocket test that ended in failure, disintegrating in mid-air soon after blast-off and plunging into the sea in a major embarrassment for the reclusive state.

As goose-stepping troops paraded in a square named after his grandfather, North Korea's new leader spoke in public for the first time Sunday -- but the message was unchanged from previous generations.

"We must strengthen our military in every possible way... and accomplish the goal of building a powerful and prosperous socialist state," Kim Jong-Un told crowds at a parade glorifying the dynasty which has ruled the country throughout its history.

North Korea has been developing a new long-range ballistic missile in a separate program from the one that led to a failed rocket launch this week, a South Korean TV station reported Saturday.

YTN quoted an intelligence source as saying the communist state carried out four tests over 16 weeks until early this year to develop an inter-continental missile at a test facility at Musudan-ri on the northeastern coast.