South Korea on Monday rejected the latest proposal by the North to hold military talks, saying Pyongyang first needed to take steps towards abandoning its nuclear arsenal.

The North's leader Kim Jong-Un offered the military dialogue during a speech to a recent congress of the ruling Workers' Party -- the first event of its kind for more than 35 years.

The North Korean military later urged Seoul to accept the offer to overcome the current "catastrophic state" of cross-border ties, proposing a preparatory working-level meeting in a message sent on Saturday.

But Seoul's defense ministry, in a response sent across the border Monday morning, effectively rejected the proposal that it said made no mention of Pyongyang's widely-condemned nuclear weapons programme, according to a ministry spokesman.

"A proposal for talks with no mention of denuclearisation is mere posturing," Moon Sang-Gyun told reporters, describing the latest talks proposal a gesture for "fake peace".

"We will firmly keep the stance that taking steps for denuclearisation should be the first priority when it comes to dialogue with the North," he said.

Most of Kim's speech at the party congress had been devoted to talking up his atomic weapons programme, Seoul said earlier.

South Korea's conservative President Park Geun-Hye insists Seoul would only consider engaging in substantive dialogue with Pyongyang if the North takes a tangible step towards denuclearisation.

But the North has repeatedly said the nuclear arsenal -- which it describes a "national treasure" -- is not up for negotiation.

Tension has been running high since Pyongyang staged its fourth nuclear test in January, followed by a long-range rocket launch a month later largely seen as a disguised missile test.

The isolated state is banned under several UN resolutions from using any ballistic missile technology. The UN Security Council responded by slapping the strongest sanctions to date on the North in March.