Kim vows 'invincible' military, slams US

North Korean leader Kim Jong-un has vowed to build an "invincible" military, as he accused the United States of creating tensions and failing to prove it has no hostile intent towards Pyongyang.

In an apparent continued effort to drive a wedge between Washington and Seoul, Kim also said his drive to build up his military is not targeted at South Korea and that there should not be another war pitting Korean people against each other.

Kim gave the speech on Monday at an event meant to mark the previous day's 76th birthday of the ruling Workers' Party.

The event featured an array of new weapons, including intercontinental ballistic missiles that North Korea has already test-launched or displayed during a military parade.

"The US has frequently signalled it's not hostile to our state, but there is no action-based evidence to make us believe that they are not hostile," Kim said, according to the official Korean Central News Agency.

"The US is continuing to create tensions in the region with its wrong judgements and actions."

Calling the United States a "source" of instability on the Korean Peninsula, Kim said his country's most important objective is possessing an "invincible military capability".

Kim accused South Korea of hypocrisy because it criticises North Korea's weapons development as provocations while spending heavily to increase its own military capabilities, including purchasing advanced US stealth fighters.

But he maintained his military does not target the south.

"I say once again that South Korea isn't the one that our military forces have to fight against," Kim said.

"We aren't strengthening our defence capability because of South Korea. We shouldn't repeat a horrible history of compatriots using force against each other."

Seoul's Defence Ministry said South Korean and US intelligence authorities were analysing the North Korean weapons displayed.

"Basically, North Korea wants to send this message: 'We'll continue to develop new weapons and arm ourselves with nuclear force, so don't slap sanctions with these as we can't agree on the double standards,"' Yang Wook, a military expert who teaches at South Korea's Hannam University, said.

North Korea has sent mixed signals toward its rivals in recent weeks.

Last month, North Korea performed its first missile tests in six months, including nuclear-capable weapons that could reach targets in South Korea and Japan.

But Pyongyang still restored dormant phone and fax channels with South Korea and said it is open to restarting official talks with Seoul.

The US has repeatedly offered talks with North Korea "anywhere and at any time" without preconditions. Kim has called such an offer a "cunning" attempt to conceal hostility.

He wants Washington to ease sanctions or suspend its regular military drills with Seoul before talks can resume.