North Korea is ready to deal with any threat from the US, leader Kim Jong-Un said Saturday as he presided over a vast parade to mark the 70th anniversary of its ruling Workers' Party.

Wave after wave of goose-stepping troops marched through the capital, followed by columns of tanks and weapons, in what may prove to be one of the largest ceremonial displays of military strength in North Korea's history.

Wearing his customary dark Mao suit, state television showed Kim receiving salutes from a commander of honorary guards before inspecting the phalanx of troops in Kim Il-Sung square.

In a rare speech to the assembled masses, a tribute to the ruling party that has served at the whim of three generations of the Kim dynasty, the leader lashed out at the United States, vowing to fight "any war" if provoked.

"Our party dauntlessly declares that our revolutionary armed forces are capable of fighting any kind of war provoked by the US and we are ready to protect our people and the blue sky of our motherland," he said.

His words were met with rapturous applause from tens of thousands of flag-waving crowds, while above the square, a large banner slung from a gas-filled balloon read: "Long live the invincible Workers' Party of Korea."

Buildings surrounding the plaza, named after Kim's grandfather and the founding leader of North Korea, were festooned with red hammer-and-sickle party flags and the national colours of blue, white and red.

A cavalcade of tanks, armoured vehicles and assorted ballistic hardware were on display at the huge march, which will be closely watched for glimpses of any new hardware that might signal a forward step in the North's military development.

The scale of the event was already apparent from satellite images taken four days before which showed a sprawling training ground in Pyongyang featuring some 800 tents, 700 trucks and 200 armoured vehicles.

When announcing plans for the "grand-style" parade back in February, the ruling party's top decision-making body had stressed the importance of "cutting-edge" weaponry suitable for modern warfare.

- Nuclear weapons -

North Korea has conducted three nuclear tests and threatened a fourth as part of a nuclear weapons and missile programme that it has pursued through a barrage of international sanctions.

There is debate among experts as to how far it has come in developing those weapons, especially the ability to shrink nuclear warheads so that they can fit on a missile.

An exhaustively researched report published this week by the US-based Institute for Science and International Security estimated that North Korea had between 10 and 16 nuclear weapons as of the end of 2014.

The report argued it was likely the country could already build a warhead to fit atop a Nodong missile -- with a range of less than 800 miles (1,300 kilometres) -- but added that the reliability of such a weapon was open to question.

Months of planning and preparation have gone into Saturday's celebrations, involving a mass mobilisation of state personnel and resources to ensure its success.

The capital itself was given a comprehensive makeover -- its streets lined and decorated with giant posters, red banners and national flags, many of them displaying the numerals "10-10" in reference to the ruling party's official October 10 birthday.

The North excels at such choreographed displays of military muscle, which aim to boost pride and patriotism at home while sending a defiant message to an international community that has sought, without success, to pressure Pyongyang into abandoning its nuclear weapons ambitions.

But they also reflect North Korea's diplomatic isolation, with Chinese party politburo standing committee member Liu Yunshan the only foreign dignitary of any significance attending Saturday's event.

Kim and Liu met for talks on Friday, during which the Chinese official delivered a letter from President Xi Jinping, and voiced Beijing's willingness to work with Pyongyang on resuming multi-party talks on its nuclear programme.

China remains North Korea's most important diplomatic ally and economic partner, even as Beijing has grown increasingly wary and impatient with Pyongyang's nuclear weapons ambitions.