N Korea's Kim defends nuclear arsenal as test fears grow

Pyongyang - North Korea's first ruling party congress since 1980 moved into a second day on Saturday, after leader Kim Jong-Un opened with a defiant defence of his nuclear weapons programme and amid fresh signs Pyongyang is readying a fifth nuclear test.

The once-in-a-generation gathering of the country's top decision-making body is being scrutinised for signs of any substantive policy change or major reshuffle in the isolated state's ruling elite.

In his opening address on Friday, the 33-year-old Kim, dressed in a western-style suit and tie, hailed the "magnificent ... and thrilling" nuclear test carried out on January 6, which Pyongyang claimed was of a powerful hydrogen bomb.

The test and long-range rocket launch that followed a month later had "smashed the hostile forces' vicious manoeuvres geared to sanctions and strangulation, and displayed to the world the indomitable spirit, daring grit and inexhaustible strength of heroic Korea," Kim said.

North Korea has conducted a total of four nuclear tests, two of them since Kim came to power in late 2011 following the death of his father and former leader Kim Jong-Il.

Speculation that the North might be readying a fifth test, in defiance of toughened UN sanctions, was fuelled Saturday by recent satellite imagery of the Punggye-ri nuclear test site in the northeast of the country.

Analysts at the US-Korea Institute at Johns Hopkins University said the presence of vehicles at the complex's test command centre signalled the possibility of a test "in the near future".

"While the historical record is incomplete, it appears that vehicles are not often seen there except during preparations for a test," they said.

Most experts have doubted the North's H-bomb claim, saying the detected yield from the January test was far too low for a full-fledged thermonuclear device.

However, they acknowledge the strides the North has made under Kim Jong-Un towards its ultimate goal of developing an inter-continental ballistic missile capable of striking targets across the US mainland.

Reacting to Kim's speech, Washington urged North Korea to abandon its nuclear weapons ambitions altogether and rejoin the international community.

"We obviously are aware of the risk that is posed by North Korea's effort to develop nuclear weapons and systems capable of delivering those nuclear weapons," said White House spokesman Josh Earnest.

"There is a path .... North Korea can take to come out of the wilderness. But it will require them renouncing nuclear weapons," he added.

The ongoing party congress is widely seen as Kim Jong-Un's formal "coronation" and recognition of his status as the legitimate inheritor of the Kim family's dynastic rule which spans almost seven decades.

Giant portraits of his father and his grandfather - founding leader Kim Il-Sung - dominated the backdrop to the podium where he made his opening speech.

The congress agenda, published for the first time on Friday, included an item on electing Kim to the "top post" of the Workers' Party.

Kim is currently first party secretary, but may take on the post of party general secretary, a position held by his late father.

Other items on the agenda included revising party rules and elections to central party organs.

Since taking power, Kim has shown a ruthless streak, purging the party, government and powerful military of those seen as disloyal, and ordering the execution of his powerful uncle, and one-time political mentor, Jang Song-Thaek.

The congress will elect its central committee which will in turn select a politburo, with Kim expected to bring in a younger generation of leaders hand-picked for their loyalty.

The conclave may also enshrine as formal party doctrine Kim's "byungjin" policy of pursuing nuclear weapons in tandem with economic development.

Some analysts have suggested Kim might signal a shift in emphasis towards the economy and, in his speech, he mentioned the beginning of a new "leap forward" but offered no specific details.