North Korea to launch top party gathering amid nuclear test fears

North Korea will on Friday launch its highest-level ruling party meeting in almost 40 years, with delegates set to heap praise on its nuclear arsenal as a "precious sword" amid fears of a fresh atomic test.

Leader Kim Jong-Un, who was not even born when the last Workers' Party congress was held in 1980, is expected to deliver a keynote address which will be minutely scrutinised for any policy shift or personnel changes in the governing elite.

The previous congress was staged to crown Kim's father Kim Jong-Il as heir apparent to his own father, the North's founding leader Kim Il-Sung.

While the agenda -- and even the duration -- of the event is still unknown, its main objective is widely seen as cementing Kim Jong-Un's status as supreme leader and legitimate inheritor of the Kim family's dynastic rule which spans almost seven decades.

The congress is also expected to confirm as party doctrine Kim's "byungjin" policy of pursuing nuclear weapons in tandem with economic development.

Ahead of the gathering, national and Workers' Party flags lined the broad, rainswept streets of Pyongyang, while banners carried slogans such as "Great comrades Kim Il-Sung and Kim Jong-Il will always be with us".

Another slogan stretched across the street defiantly proclaimed: "Defend the headquarters of the Korean revolution at the cost of our lives."

Since Kim took power after the death of his father in December 2011, North Korea has carried out two nuclear tests and two successful space rocket launches that were widely seen as disguised ballistic missile tests.

'Credible deterrent'

Even as the international community responded with condemnation and sanctions, Kim pressed ahead with a single-minded drive for a credible nuclear deterrent with additional missile and technical tests.

There has been widespread speculation that the congress would be preceded by another nuclear test in a gesture of strength and defiance that would allow Kim to claim genuine nuclear power status.

Ruling party newspaper Rodong Sinmun this week described the nuclear arsenal as a "precious sword", and said the weapons were a "treasure of all happiness that will ensure many things in decades to come".

But the evidence of an imminent test remained inconclusive. Analysing the most recent satellite pictures of the test site at Punggye-ri, the US-Korea Institute at Johns Hopkins University on Thursday said there was no clear evidence one way or the other of whether an underground test was imminent.

South Korean government officials believe the North is ready to conduct a test as soon as the order is given, and say a decision might have been taken to test during the congress, which the world's media have been invited to cover.

Officials in Seoul say they expect the event to last four days, with the opening day devoted to Kim's speech and a lengthy report on the party's achievements.

Some analysts predict significant personnel changes as Kim brings in a younger generation of leaders, picked for their loyalty to him.

Preparing for the congress involved mobilising the entire country in a 70-day campaign that New York-based Human Rights Watch denounced as a mass exercise in coerced labour.