North Korea is “ready to hit back with nuclear attacks” if US takes provocative action in the region.
“We are prepared to respond to an all-out war with an all-out war,” said Choe Ryong-hae, believed to be the country's second most powerful official, reports BBC.
The comments came as North Korea marked the 105th anniversary of the birth of its founding president, Kim Il-sung.
A huge parade in Pyongyang was held amid speculation current leader Kim Jong-un could order a new nuclear test.
The displayed hardware appeared to be new intercontinental and submarine-launched ballistic missiles.
The show of strength comes amid mounting tension, with a US aircraft carrier group steaming towards the region.
"We are ready to hit back with nuclear attacks of our own style against any nuclear attacks," he said.
Rows of military bands and goose-stepping and sword-wielding soldiers marched through Pyongyang's main Kim Il-sung square for the "Day of the Sun" celebrations, as a black-suited Kim Jong-un watched on.
He saluted an honour guard and took his place on the podium. At times he appeared relaxed and laughed with aides.
Military planes created the number 105 in the sky.
With concerns that North Korea is getting closer to successfully producing a nuclear arsenal, Saturday's parade was an opportunity for Kim to broadcast North Korea's current military capabilities.
On display for the first time were what appeared to be the Pukkuksong submarine-launched ballistic missiles (SLBMs), which have a range of more than 1,000 km (600 miles).
Weapons analysts said there also appeared to be two new types of intercontinental ballistic missiles (ICBM) in canister launchers, but it remains unclear whether they have been tested and Pyongyang has yet to announce it has an operational ICBM.
The nation's aim is to be able to put a nuclear warhead on an ICBM that can reach targets around the world.
It has conducted five nuclear tests and a series of missile launches in pursuit of that goal.
Pyongyang has claimed to have miniaturised nuclear warheads for use on missiles, though experts have cast doubt on that given the lack of evidence.
Saturday's military parade made clear how vital the state's nuclear programme is to its future ambitions, as it continues to ignore growing pressure from the US to abandon its nuclear weapons programme.
On Friday, China's Foreign Minister Wang Yi warned that "conflict could break out at any moment", adding that if war occurred there could be no winner.
Unlike at previous Pyongyang parades there did not appear to be any Chinese representatives present.