The North's decisions were made in a meeting of the ruling party's full Central Committee which had convened to discuss a "new stage" of policies.
Pyongyang has made rapid technological progress in its weapons programmes under Kim, which has seen it subjected to increasingly strict sanctions by the UN Security Council, US, EU, South Korea and others.
Last year it carried out its sixth nuclear test, by far its most powerful to date, and launched missiles capable of reaching mainland United States.
Analysts said the move announcement was significant but noted the regime was not ruling out future tests.
"The precise language here is important," said Vipin Narang, a nonproliferation expert at MIT.
"Closing the testing site doesn't preclude atmospheric nuclear tests for example (or other sites). And missile tests could still be conducted under the guise of space launch vehicles."
This article originally appeared on the Daily Telegraph.