Kim Jong-un says nuclear weapons ready for use at any time

North Korean leader Kim Jong-un has said the country’s nuclear weapons “need to be ready for use at any time” amid rising threats from enemies, according to state media.

Kim has told military leaders to be prepared to launch pre-emptive strikes as he supervised training involving newly developed rocket launchers, the Korean Central News Agency reported.

"Now is the time for us to convert our mode of military counteraction toward the enemies into a pre-emptive attack one in every aspect,” Kim was quoted by the news agency as saying.

"At an extreme time when the Americans... are urging war and disaster on other countries and people, the only way to defend our sovereignty and right to live is to bolster our nuclear capability.”

His remarks come after the United Nations imposed tough sanctions against North Korea for its nuclear programme.

North Korea on Thursday fired six short-range projectiles into the sea in response to the sanction.

It’s not the first time Kim has warned of pre-emptive attacks on its enemies, having previously threatened South Korea and the US.

However, military experts are uncertain whether North Korea has yet developed a long-range nuclear bomb with a miniaturised warhead to reach as far as the US.

Still, Kim’s announcement prompted a response from the US.

"We urge North Korea to refrain from provocative actions that aggravate tensions and instead focus on fulfilling its international obligations and commitments," Pentagon spokesman Commander Bill Urban said.

The US and South Korea on Friday started talks on the possible deployment of a US missile defence shield in the South.